If Darth Maul could survive plummeting down a bottomless shaft with his lower half missing, then Mace Windu has a high chance of still being alive.
Remember, in Star Wars falls from great heights never killed anyone:
Obi-Wan Kenobi (EP II Kamino, also EP III Order 66)
Luke Skywalker (EP V AND he had his hand chopped off like Windu)
The Emperor and Boba Fett (who both came back in the EU)
Obi-Wan survived due to Jango's whip cord and even if he did fall all the way it isn't falling for miles down, in Ep 3 that wasn't really a long fall and he just fell into water.
Yes but Luke wasn't also fried with Force Lighting, that is what killed Windu and infact Luke would have died if he hadn't been sucked in through another portal vent.
The Emperor came back due to Essence Transfer(or rather cause authors couldn't figure out a new enemy), and Boba didn't fall a huge height he fell into a sarlacc pit which he shouldn't have gotten out of due to the biology of the beast but came back due to fans, the same with Maul and the fact that TCW was wanting to have another villain come into the story.
So...ya, the only one you could say that for is Luke and he would have died had he not been sucked into another vent.