Very interesting. Just watching that gives me hints that they might end the anime, without a 5th generation for it.
Ash we know has this connection with Ho ho. He saw it just when he left, on the first ever episode. This movie could wrap things up very nicely indeed for Nintendo/the writers if they wanted to. Ash catches Ho oh (unlikely probably) or Ho oh reveals to Ash that it's been following it... spiritual bond... sacrifices itself (you know the rest, this is definitely more likely). If they play their cards right, and end the TV show just before it with him winning Sinoh and then meeting up with everyone again, Misty, Gary, Oak his mum, all his old pokemon etc and then release the movie it would certainly work and would give most of the fans a satisfactory conclusion to the anime.
I do have to say the trailer looks epic so I can't wait for it to come out, whatever the consequences of that are.