Confirmed so far:
>Meowth
>Luvdisc
>Corsola
>Slowpoke

Featured in concept art:
>Blastoise line
>Furfrou
>Wobbuffet line
>Machop line

I'm looking forward to seeing Meowth as it's not been featured in any regional dex since Johto. I never used it because its moveset was shit, hopefully a few gens later it'll be more fun to use in-game.

There's a few Unova mons we didn't see in Kalos or Hoenn, like Vullaby, Blitzle and Sewaddle, that I think could work well in Alola.

I'm also hoping to see forgotten mons like Mankey, Venonat and Stantler.