I see it somewhat like this.
Maul climbing up the bottomless pit and getting his body restored. Then being tired of Sidious wanting ultimate revenge. He would meet up with grievious and duel. Eventually Maul would tire out and come to the last resort by throwing his double bladed lightsaber at grievious and killing him for good.
Unfortunately I dont think Maul will be facing Grievous or any Jedi aside from Ahsoka. Filoni and Pablo went over the Siege of Madalore arc at Star Wars celebration 2016.
And (spoilers) Kenobi and Skywalker are called away to rescue the Chancellor (beginning of Revenge of the Sith), but Anakin leaves Rex and half of the 501st to back up Ahsoka in toppling Maul. They also have Bo Katan and her Mandalorian soldiers on side.....
All That said it pains me that in these post TCW/SOD days that there are still people who rate Grievous =/> Maul.