I had really high hopes that Chesnaught was going to be a playable in this game, but considering that the game is being released in 3 days, the odds of more characters seems highly unlikely; unless of course, there were to be some sort of update or a Wii U version.
The little theory I had of Chesnaught making an appearance was because of how both Fennekin and Frogadier (different evolutionary forms) have made their presense in the game as supports, and we've seen absolutely no sign of the Gen 6 grass starter. A Chespin evolution form could make a support appearance as well, but I personally see it to be more fit for there to be playable Chesnaught. Aside from Chesnaught's fighter-like appearance, he would play as a defensive kind of pokemon, with moves such as Wood Hammer and Spiky Shield. There's also no hint of a grass type pokemon nor a Gen 6 as a playable yet, so it would make sense overall to have Chesnaught in Pokken Tournament.
Let's hope for more characters!