I know some don't consider it canon nor like any single thing about it, but the return of Darth Maul in cybernetic form in Seasons 4 and 5 of The Clone Wars
happened after Maul was not only sliced clean in half by a lightsaber but also after his remains tumbled down an extremely long and deep plasma shaft in the Theed hangar facility on Naboo. Who knows what he might have fallen into when he finally reached the end of that fall in addition to being cut in two and most likely being in some sort of shock.
If Darth Maul could continue to live after losing every inch of his body from the six-pack or navel down then it's sure not out of the realm of possibility that Mace could have somehow survived even after the barrage of Sith lightning and long, acrophobia- or vertigo-exacerbating fall. I'm still inclined to think that the Clone Troopers acting under Order 66 got him even if the fall didn't, but in the Star Wars
universe there've been characters who've managed to survive worse and emerge more badass than before.