Why? Because everyone will migrate to D2?

i doubt it would, there should still be a decent size of players for a good amount of profit. However I'm sure both Bungie and Activision will feel the effect$ of the reduced population in comparison to the release of D1. You may see Activision forcing Bungie's hand to shape D2 through its expansions and patches to be like D1 again, for more $ of course. I say this because look at their response for CoD when sales and public outcry were very negative, they returned to the old ways (WW2) yet I bet they kept the methods of which they use to suck a much $ out of every player's wallet.