>>39096399there's a distinct chance it will only be charizard, an egg given to you sometime before or after the champion fight, like rse and beldum. starters are generally otherwise unavailable except through some kinds of in-game events or cross-gen trading. we'd have to meet npcs who'd progressively offer a new one from each generation like xy and the second starter coming with its mega stone, or to go back even further with pokemon yellow and completing milestones like number of pokemon caught to get bulbasaur or number of badges earned for charmander.
If they keep hidden abilities as a thing, we might get some of the unreleased ones if there are any. I wouldn't hope for it, though.