It's weird that they chose two Pokémon from Gen 2, but it's understandable. I guess they had to avoid Kanto & Hoenn starters because of the already existing megas, the Kalos starters because they'll likely be all available, starters from the latest games because they're too new, and Sinnoh starters plus Cyndaquil and Oshawott for obvious reasons, so their options were pretty limited. At least one Johto and one Unova starter were basically guaranteed, also those starters didn't suffer much from overexposure (poor Snivy though...)
I imagine they'll give something new to Meganium, Emboar, and Feraligatr. I hope it's a regional form and not a Mega evolution, because regional forms are pretty much guaranteed to make their way into the main games, but megas will likely remain stuck as a niche for this game due to being incompatible with each gen's new gimmick.