I don't see how this can be anything other than 8th gen, new generations sell gangbusters and have more creative freedom than other types of Pokemon games, so they're a good game to start out with since they draw in a huge audience and show what the new hardware can really do. The more interesting question is what will this game be like? Reggie said it would be a traditional "find, train, battle" experience but that doesn't mean they can't shake up conventions in the series. And with this being the first console Game Freak is developing for, bringing with it much stronger hardware than they've used before and a new audience that has never played their games, I'm wondering just how much the series is going to evolve. I wouldn't be surprised if this ends up being open world or similarly open ended, that is the kind of experience console gamers tend to gravitate to and there's been a lot of praise for BotW and Mario Odyssey having a similar type of shake up, so it might be a good idea for Pokemon to take a similar approach as well.
