Spoiler from EP3, he died
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)