While totally conceding the part about younger players being more likely to be spurred into comp sci by video games I do contest the hardcore games as a gateway drug theory. I think the thing that pulls kids in is the creativity of the games and the effect that the game has on them. So a fun casual game in my opinion would have the same pulling power as the latest version of crysis. fwiw this is subjective and I dont have any data to back this up.

One further point - maybe the 40% number is a recent phenomenon and it will take time for it to translate into more women entering computer science.