Quite correct. Hackers found out about those moves before B2W2 were even announced as data for it was found within the game code for BW. While this time around hackers won't be able to do anything with a dumped rom for at least a good while, the point still stands - if they want to bring in new things within the same gen such as moves or Pokemon, data for it needs to exist with X&Y.
The 3DS should be better than the PSP. But that doesn't bypass the fact that a game will simply be unable to show the player a Pokemon if there is no data within it for said Pokemon. And said data is required in trades and wifi battles. And to hide a large number of Pokemon within X&Y to be revealed only in later games is a very strange choice for them to make, you have to agree. Mega forms, perhaps, but brand new Pokemon? It's really a big stretch to make.
Frankly, one is just going to have to accept that we have 'only' 70 new Pokemon. That's not a small number in itself - just smaller than previous generations. And that's excluding mega forms, and excluding event Pokemon, the only ones which have been traditionally hidden away. This time though for a change, we actually won't know about them for some time!