I know the number is 70, or thereabouts. What I disagree with is that you say they have to introduce 100 pokemon minimum. That it is the sole point of new Pokemon games. This was never a requirement, nor should it! Just because it has been in the past generations doesn't mean anything. BW for instance did not get a third 'grey' version for instance, despite the history of 1st-4th gens having such a game.
The 'point' of Pokemon games? It is to make more money from a successful franchise, simple as that. That's the way Game Freak views it.
Besides, 4th gen, when you remove the number of Pokemon tied to previous gens (Weavile, Togekiss, etc), falls below the 100 number, so there you go.