Note my avatar-- do you really think getting his hand cut off, being zapped, and falling out a window would be enough to take Mace out for good? If Anakin can free fall through a freeway and land on a car, so can Mace. ;)
Also, Boba Fett is so tough, that the only way to defeat him in ROTJ was by a freak accident involving a blind man. Everyone knows that he blasted his way out of there a few hours later, though. ;)