lets look at dmc4 as an example
the first 3 were all ps2 exclusive and and capcom didn't even think it would affect sales at all.
then ninja gaiden came along and sld decently well showing there was a good hack and slash audience on 360
now dmc4 is multiplatform and the 360 will acount for a large part of its sales maybe even 1/3
if the rpg games like lost oddyssey can have the same effect we can see more mutiplatform rpgs
dont veiw it so black and white its a complicated industry