Actually, since this Direct is for 3DS owners in general, and not just Pokémon fans, revealing something major like the return of Megas or details on a new feature would seem more effective to show. Just one new Pokémon or Alola form would certainly please Pokémon fans, but they already have a slew of announcements to look forward to on Pokémon's Youtube channel. But 3DS owners who aren't interested in Pokémon will need more than just a Pokémon or recolor to get them interested in the titles. Since you have to go out of your way (and as such, already be a Pokémon fan) to make use of the Pokémon channel's announcements, this Direct is Nintendo's chance to try to broaden the appeal of SM to 3DS owners who still haven't jumped on board. So I feel as though if they do show something, it would probably be more like a feature that they think would appeal even to people who aren't or haven't been interested in Pokémon. I mean, they could reveal a new Pokémon, Alola form, or starter evolutions, too, but those by themselves likely aren't going to convert non-fans into getting the games, so this is really their best opportunity to detail a major feature or facility, if the game has any.
As for gen 2 on VC, Pokémon never celebrates the anniversary of non-gen 1 titles (or rather, they haven't in the past). So the pessimist in me can't imagine they would care enough about gen 2 by itself to celebrate its 20th anniversary ("2019 marks the 23rd anniversary of gen 1!"). So, might as well release them on VC when they're ready. Being able to transfer Pokémon from gen 2 VC into SM would definitely be another selling point for SM, at least.