Would've said 
and 
but just recently got some passive changes and they usually don't do that when they're going to work on them again in a couple months.
And actually around this time in the process they are already doing early/preliminary work on the next VGUs
So my guess is and 
P.S. I secretly wish 
was next. Cannot wait for this guy to become the badass he has the potential to be
I don't know, it could just as well be Akali or Irelia up next, or some other Tier 1 champion. I'm not so sure they'll want to VGU two Noxians in a row (Urgot then Swain), unless their past trend of "align VGUs with regional lore updates" is not something they want to keep doing moving forward, or unless (crazier thought) Urgot is no longer Noxian. Ionia on the other hand hasn't been touched on in quite a bit lorewise, so it seems ripe for an update both narratively and champion/gameplay-wise since some of its champions are outdated and problematic.
I also want Pantheon to be reworked, I feel you fam. There is always the Ryze possibility, where even though the champion is in a good spot, they rework them anyways because of fleshed out direction in the preliminary development.
Right now we could assume all of the Tier1 champs are being looked at, the ones they probably are considering are the really bad ones, gameplay wise (even among Tier1) and the ones with grounded direction for their character (Irelia's telekinetic swordstyle archetype and Pantheon's god of war stereotype are the big contenders here, although only one of the 2 may be chosen to squeeze in early).
Riot also stated that by doing class updates on a champ that needs a VGU they are fixing them for a year or two, which is why champs such as Malphite and Rammus weren't really touched in the tank update (they don't want to waste resources on something they plan to tackle not far from now) we saw champs like Swain, Akali and Shaco, even though slated for VGUs, get dome love in the past class updates, if this means that they are being pushed to the back burner of the Tier 1 champs, idk, we will have to see if Panth and Irelia see changes in a possible Diver update this coming preseason, or if they are also ignored.
had some smaller changes in the middle of last year. Plus it's not gonna be a "couple of months" . 
for one has been in the works for around 4-5 months, and usually takes 6-8 for the reworks to be completed. So we've still got time.
Since the next champions are Urgot and Eve, which kinda represent the factions Noxus and Shadow Isles, I kinda doubt it. I don't think they would chose the exact same combination of factions 2 times in a row. At least as long as Urgot keeps his ties to Noxus.
Personally I would prefer Rammus to get an update. His kit is in a worse state than Swain in my opinion because alot of its potential is limited by the enemy doing mistakes. If the enemy is not attacking you, you are not as useful as Rammus. And they introduced alot of mechanics the last time which just naturally could blend in Rammus' rework. The movement speed scaling from Warwicks ult could get implemented in Rammus Q, he surely should get an ad shield (which they introduced with Camille). And so on.
I would find it kinda strange that they have these elements now in the game and don't immediately use it to update Rammus. And his model needs serious work, too. He is not the slightest looking like on his splash art.
