Darth Maul, Emperor Palpatine, and even Kylo Ren (temporarily) came back after falling into the abyss, and with Windu’s body never recovered, it’s certainly plausible.
While Mace Windu is presumed dead at the end of Revenge of the Sith, Star Wars has proven many times over that it takes more than a great fall to kill a Force user.
Plus, there’s now a thought that someone had to rescue or know of Grogu and removed him from the Jedi Temple before Order 66, and as a member of the Council he would certainly be aware of that situation.