From all the things going on:
, plus the crazy amount of %HP true damage 
changes making her go mid lane
Since they officially destroyed the "tank meta", ADCs no longer need to worry about a wall in the way.
Anyone can duel anyone
Let's get one thing straight here: Nearly every season so far has been a marksman meta. Your team comp will 99% of the time contain a marksman of some sort, and it's been that way since season 1. They are not optional like other roles.
Tanks come and go. Assassins come and go. Mages come and go. Bruisers come and go. Fighters come and go. Marksman are forever.
Im going 
Top to abuse that "shotgun blast to the face is solution to all my problems" thing. And to be able to say "I came here to kick ass and smoke cigars, and Rito took all my cigars."
On a serious note, all of these AD items can also be abused by Assassins except for a select few.
We will have to wait and see if your prediction is true but I think it's fair to say that RIOT has a track record of favoring the ADC's over other roles so I wouldn't be surprised if we see tanks go away again... not that they ever managed to make a full comeback in S5 in the fist place...
Is it just me, or will the ad item changes make AD Malzahar scarier?
been ADC meta since season 1, ADC mandatory every game
Tank player here. Put up with this bullshit since season 2. I'll give preseason the benefit of a doubt, but if we get to season 7 and OP is right, I'm done. I don't enjoy playing marksmen. I don't want them on my team. I don't want to play against them. I'm tired of being crit for a 1000 from 700 units through 200 armor. Tired of them soloing my turrets without a minion wave. Tired of them taking dragon and baron easier than my junglers. The amount of favoritism is absolutely unfathomable. No other class is coddled like ADCs, none.
Curious to see what happens when the dust settles, but worst case scenario I uninstall this game.
And now they can't be bursted Death's Dance
It's looking like most games will be 5 Marksmen vs 5 Marksmen. With the reworks, masteries, and new items, they really don't have any glaring weakness.
Well actually "ADC's don't have to worry about a wall" is kinda weird thinking, because ADC's are the primary killers of tanks.
I wonder what you mean by anyone can duel anyone, because random examples that come to my mind are a melee kiteable champion trying to 1v1 a Kalista or a Vayne ; or a Soraka trying to 1v1 a Yi. Doesn't end well in either case.
ADC meta since season 1, but never has there been a meta where 4 ADCs + 1 support was possible.
Until now.
Sure this comp is lacking and squishy, but it is at least possible to use and not feed horribly. That itself is worrying.
next season, a void dragon will spawn in the center of the sr's map and support items will make it possible to have a pentasteal for the support, something like "if you buff an ally with this, every kill he gets (in 40 secs) is yours" =D
Oh please. I remember when Riot made marksmen optional, in the juggernaut meta. Yeah, you could even replace your marksman with a juggernaut and win consistently!
However Mordekaiser has not been well received...
My point is you can't say it will be a marksman meta. ADC were more or lessv required for years. We're finally in a time where an alternative exists, and most board posters are trying to force the one bot lane melee carry into a solo lane.
For all we know Illaoi is a bot lane juggernaut!
Edit: I should also mention how pissy people get when you try to take Quinn Top. It's understandable seeing as top and jungle is usually where tanks go. You make it seem like this marksmen meta will have marksmen all over the place when, from my experience, people don't even want a marksman jungler because they already have one in bot lane (and refuse to change comp accordingly).
Graves top, Quinn Mid, Kindred Jungle, Caitlyn Bot... Sounds like a terrible, terrible teamcomp. They're going to pick one adc, and send them bot lane, until Pro players do it differently.
WTF is this "tank meta" you speak of?
You DO realise that now shreds bonus armour, not total armour?
