Well on my PowerBook G4 I could not hear the fans at all while playing WOW, and the fans were almost silent on my First Gen Mac Book Pro - although after playing for a while it got very hot. I was hoping with the changes Apple made to the graphics card/ processor/ backlighting that it generated a lot less heat than the previous model.
There aren't any changes that Apple made that would contribute to a lot less heat. The GPU is much more powerful than the X1600 (and note that the X1600 in your first gen MBP was dramatically underclocked compared to the C2D MBP's X1600 even), the CPU's are just faster versions of the same line, and I don't think the switch to LED-backlighting would affect the heat generated in the internal chassis, really.