Coro Coro revealed some more information on Pokémon Mysterious Dungeon’s, not long before its release in Japan (November 17). It looks like the three legendaries: Articuno, Zapdos and Moltres also appear in the games. Have a look at the scans by yourself: scan #1,scan #2 ,scan #3. Expect more updates soon!
In case the links above don’t work try Filb.de or Bulbapedia’s related articles.