Of course it's only preseason so we can't really know where the meta is headed. However certain things seem to strike out so here is a thread about guessing(not predicting) which classes and champions will be dominate
Early game dominance. Lee Sin, Shaco, and Pan will dominate. Late game AP mages will decline in popularity since games are ending faster.
Once LCS hits people will realize how much of a tank/fighter meta we're actually in, imo.
I just can't wait to see Thunderlord's LCS
The meta is headed to 
All Hail The META lord.
Corki will be pick or ban, or at least an extremely contest pick.
Where the meta is oriented?
are already super strong these days and they will get a new item just for them, so ad assassin will just be super duper op, like they aren't strong enough already. So yeah, ad assassin's meta.
Ao Shin is going to DOMINATE
League of Thunderlords
the trash because china owns this game
Riot undoes Quinn rework, fixes bugs and implements suggestions from long-time Quinn mains, becomes Tier 1 but strong not OP.
InAPerfectWorldWherePlayersActuallyMatteredToRiotsChineseOverlords
My bet's on the meta becoming assassin and ADC centric after a few outlier champions (Mundo) are nerfed.
Right now ADC itemisation is actually insane, and the LW upgrades are getting buffed, dispite the fact that Lord Dominik's deals more damage against tanky champs than old LW ever did. There's going to be no reason to play tanky champs once this happens, duel ADC teams will be picked up to melt tanks whenever they're picked, since they'll be able to melt through the tank in a matter of seconds. If you're wondering how you run multiple ADCs Ez and Corki have historically been played mid, in theory the new Graves and Lucian can also work.
With tanks flat out not being able to answer ADCs most mid and top laners as well as junglers will move to the next best possible answer, assassins. I'd expect to see huge hikes in the play rates of assassins and assassin like bruisers and mages.
Top lane will probably shift to champs like Irelia, Fiora and Quinn. Poppy is also a possible competitive top laner since she has reasonable anti ADC traits and specifically counters the incoming assassins, even although she doesn't have very many assassin like traits herself.
Mid will most likely shift towards champs like Ekko, Zed, Dianna, LB and Talon. It mostly be dominated by true assassins, but there's room for specific mages to see play as well. Azir would be my top prediction, since once again he has specific anti assassin traits and he also is a fairly strong lane counter to most melees, which most assassins are.
Jungle will be the standard shit it devolves into when tanks aren't particularly good. Lee, Nidalee, Rengar and probably some of Eve, Rek'sai, Elise and J4. I don't think that this on needs to be overly justified, it's pretty much just what happens when Riot screws around with the jungle and does something stupid like splitting the starting jungle item into two.
Basically I'm predicting a complete shitfest meta, because the last time I saw Riot have a heavy emphasis on diversifying AD items was at the start of season 3 and I can only make predictions based off of what I've already seen.
Support Kog'Maw is a thing now, so I guess anything can happen.
Edit: All speculation about meta shifts before the preseason proved itself to be false, too.
Immobile mages and everything that hasn't been nerfed already in 6.1.
Fuck mages and juggernauts.
Whatever class gets reworked next will be the next target of complaints.
23/0/2 Supports
But in all seriousness, I think that AP mages will dominate hard. It's kind of a given since they already mentioned tons of time that they will rework them (For Riot, Rework = accidently overbuffed, oops, sry). After the whole AP mages meta settles down, then I think they will take a look at the jungle and junglers
(only my opinion) Fervor of battle in the pbe has 112 max damage and only takes 4 hits on a melle to stack that is huge. I am guessing bruisers like jax and xin and assassins like yi,riven and sin will greatly utilize this. Top lane will probably mostly be bruisers and tanks that scale well with armor or reduce damage from hits. Rammus may be a sleeper choice for top lane.
Assassins dagger seems very powerful if it gets released. The plus side on a mid ad assasins with this is they can reserve ignite for after zhoynias. The nightfall proc will do a ton of damage 25% missing health is like a ignite on its own so people will have to zhoynias that.
You can also trade ignite for teleport and lessen the affect of starving. This i think will make ad assasins meta for mid lane
Carry junglers are making a huge resurgence in the current meta; I think we'll see a lot more in the way of multi-threat comps and supports with huge amounts of security or disengage. I'm not sure that the Alistar/ Annie engage will be very viable anymore because they'll need to be held back for peel.
It wouldn't surprise me to see full teams without a dedicated tank or teams that have no control mages due to security issues.n There just isn't time in a game for AP scaling anymore, so I would bet we're looking at meta full of AD carries (not necessarily marksmen) and melee AP characters in every role.
Bruisers and Tanks will dominate, not sure why, I just feel they will.
Runic Echoes will likely soon replace Runeglaive.
After the new AD assassin item comes out, people will probably start spamming AD assassins in mid lane..
Top lane is still primarily filled with AD fighters and tanks.
Tank supports are still prominent picks.
Fast meta seems most likely, with really prominent early game junglers, Lee sin, elise, mundo is my dark horse jungler,
Top lane reverts to season 2s Holy trinity of top laners, shen, jax, and malphite
Mid will either be assassins or wave clear focused mages to protect towers
Bottom lane will be aggressive as fuck with tank supports like nautilus and leona and mage supports like annie brand dictating the pacing, other strong marksman like, lucian, jinx, cait, and tristana will be staple
Or until people discover how rediculous corki is
It's gonna be a really fast, snowball meta
By week four of the LCS I bet the Meta will be right about where it was right before the Juggernaut changes, or maybe closer to the tank Meta. there might be some differences in champs here and there, but I see it just starting back somewhere between the tank and juggernaut area. With all of Riot's changes, the nerfs to some of those changes really just put it back to where it was meta wise, outside of faster games.
Let me explain.
Only a few ADCs are realistically at the top, so you'll see the same 3 with 1-2 outliers for specific comps or preferences (like Dlift with trist for example). If you see Kog and Graves more than a couple of times it will be specific comps, and likely on the losing end. Lucian will be the top ADC without a doubt.
Tanks will be strong and wanted, specifically CC tanks, because of the early prevalence of assassins for a few weeks. Illaoi and Mundo will be on permaban for a bit until one or both get nerfs (guess we are already there) with some outlier jungle picks like Rammus/Malphite, but still the same Lee Sin/Nidalee (with rengar now added to that). Supports will likely be relegated to tanks as the junglers will be for the earlier ganking.
Talon will be a popular pick for maybe a week or two then Riot will remember they hate him and nerf him again, while not touching Zed (who will be one of the top picked mids for most of the split) and Yasuo won't be far behind. We will see the return of heavy wave clear mids as well, like more Anivia, maybe the occasional Ziggs, and I foresee Orianna coming out earlier in the season instead of closer to worlds like normal. I also expect to see some Morg mid again from a few teams here and there.
Blue trinket is still going to be the go to for most laners out of laning phase, unless yellow gets considerably buffed (no surprise there).
Top lane will consist of Jax/Renekton every time they are up. 
will likely get further nerfed because of just Jax, because that's how riot logic works.
Supports will likely consists of tanks and CC (Ali, Nautilus, Braum, Tahm effing Kench) and fewer mages/squishy utility until the assassins start being less prevalent in about week 6-7.
