@The_Djoker To answer your question, Yes and No. For one thing we don't know how many Pokemon will be catchable in this game at this point in time.
What we do know is all of the 600+ Pokemon from Generations 1-5 will be in the Pokedex as well, you'll just have to do a lot of trading with those who actually played the past games to get any that aren't available to catch in-game.
Looking forward to Pokemon X and Y. White FC: 0862-2660-4156 / 3DS FC: 2492-4470-1418 / White 2 FC: 4556-7836-2644