If Darth Maul can survive getting sliced in half and falling down a bottomless pit (which I think is dumb, mind you, but like it or not it is canon), if Anakin can survive getting all his limbs cut off and third degree burns over 100% of his body, if Boba Fett can survive getting digested by a sand monster, I think Mace can survive getting his hand cut off and getting tossed out a window. Considering that is pretty much exactly what happened to Luke in ESB. And considering he is a powerful Jedi and I don’t find it that hard to believe he could use the force to grab onto a ledge or land on some speeder flying by below. I wasn’t convinced he was dead seeing the scene for the first time.