For those of you that have FSX, here is the info from the "Horses Mouth" translated so that we can all understand it (Adam speaks a VERY technical language!)
Would be, but again, won't happen. Dual Cores would not give any real additional performance because of the way FS is designed and the way Dual Cores run. There was no way to maintain backwards compatibility and get Dual Core optimization that gave any real increase in performance.