Since Articuno and Latias are legendaries, they might be included as special post-game events, like in the newer games. I would love for Houndoom/Houndour to be included, he is a beast! Vulpix and the Ghostly family are pretty nice, so i hope for their comeback as well.
Some other interesting questions:
How large do you think the National Dex is going to be?
How many of these will be new Pokemon, how many old ones??