A year doesn't seem too likely; two teasers for mainstream attention seem to suggest a much closer availability date, especially coupled with exilecon being included in the teasers and GGG's implication that you want to leave for home pretty immediately after the convention. I'd expect the start of some kind of beta a month or two into the next league, with an aim to release for the winter league. Granted, that might just be wishful thinking on my part, but it seems a sensible way to capitalize on the hype they're building.
Yeah I'd wager we at least get the beta before summer next year. Probably in either next league, or the league after somewhere.
Edit: Although who knows if it's going to be a Beta, like there's 3 acts available, it's a voided side-mode to normal PoE, etc, or if it'll be a "Beta" where it's integrated with the main branch and we start getting many, but not all, PoE2 features in PoE.