Return of the musclecars! It's happening all over again. First the mustang, then chevy gets in, then a mass of high power, rear drive v-8's rock out.
As for the banshee, the 450 is most likely replacing it. However, if a suitable replacement were made, it would have to live up to the banshee. High revving, massive power, sweet sound,etc... 2-stroke is out of the question for emissions and C.A.R.B. and whatnot. I guess an inline four, maybe gsx-r motor? Fuel injected, quick revving, high power four banger four stroke.
IMO, the only replacement for a banshee could be somethig as wild as a production gixxer six motor in a yamaframe, maybe even some modern suspension?