Maul survived. Lucas realized he made a terrible mistake by killing him. Apparently it panned out pretty well- I haven't watched all of The Clone Wars.
It's starts out terrible and gets progressively better.
He has, like, 4 separate appearances, and in each one, he's a much better character.
He starts out as just, like, a gibbering lunatic attached to a metal crab. Becomes a growling monster with giant Grievous legs in his next appearance. Then eventually, he gets regular looking cybernetic legs, and gets his **** together and becomes a much more methodical, calculating character, and actually manages to accomplish some things besides just ranting about Obi-wan.
And, in those appearances, he gets into 2 of the better lightsaber fights of the series:
I like this one because Maul didn't used the force and kept it skill vs. skill.
I'm curious if they'll go into what happened after Sidious captured him.
Well, they already did go into what happened after Sidious captured him. See the Son of Dathomir miniseries by Dark Horse, which is still canon. Would've been a cool arc. Mandalorians vs Battle Droids. Maul vs Dooku. Vs Greivous. And Talzin vs Sidious. The sad thing, the arc pretty much exists to eliminate Maul's Shadow Syndicate (probably setting up the Siege of Mandalore with the Death Watch) and puts back into Sidious's captivity.