It's going to be a Tekken-style Pokémon fighting game. The only characters shown in the trailer are Lucario (who Mega-Evolves at the end) and Machamp, though a leaked image from a while back showed Blaziken as well. Other than that, there's not much info here other than the game is coming to Japanese arcades next year.
This looks like it could be really cool. I'm not really that big into Tekken, but I could see myself getting this. I would think it'll be released internationally on the Wii U at some point.
But wait, there's more! Later that night, Nintendo announced 2 DLC packs for Mario Kart 8 coming this November and next May. Both packs will have 3 characters, 4 vehicles, and 8 courses (2 tournaments).
So yeah, yesterday was a huge day for Nintendo news. Hopefully we'll get a Nintendo Direct soon so we can get even more news and hype!
HBM, signing out!