Yes, he voiced MX, but his passing won't affect the story at all. They'll just hire a new voice actor.
Whether or not Terra will get his body back will be determined in the Xehanort finale, Kingdom Hearts 3.
....Dude I know that, I was making a stupid silly joke.
Seriously I'm amazed you thought I was serious and not making a stupid silly joke. Even my brother who also said the exact thing you just did too but at least he understood where I was going with it too, he got the joke and chuckled a bit. And our sense of humor don't intercept all the time either you have to understand, so seeing him laugh a little felt kind of good. I actually even made an entire room laugh with that stupid joke believe it or not yesterday when I went to Will's birthday party yesterday and told it, because they understood it was a joke and could see I meant it in like some kind of comical fan fiction situation with like say Xehanort fading from existence or just suddenly pop. I mean it in a fictional sense not a 'Oh the actor's dead let's just get rid of the character' way, they can't do that in a video game like they do in a say live action show, or if he was just voicing some minor character.
They obviously didn't do it when Eggman's previous actor died, Scott Drier I think it was, and replaced him with Mike Polluck, so why would they do it here? Of course they would get a new Actor for Xehanort, that's the obvious thing to do, that what they will do and it would be stupid if they didn't. It doesn't matter if Nimoy was much more famous than Scott Drier, Xehanort is integral to the story so he has to be replaced. Not to mention if they were stupid enough to do that it would kind of go against one of Nimoy's most famous quotes as Spock and from what I've seen of his Twitter about his offer to become anyone's honorary Grandpa, and his book I am Spock after people got confused with I am not Spock thinking he resented his role of being Spock and not the fact that his role of Spock made people Type Cast him because he understood that people cared about his character as Spock a lot I think it's something he himself lives by. "The needs of many outweigh the needs of a few."
However when I saw that he voiced Xehanort that joke was the first thing that popped into my head because my imagination felt it was appropriate to make a silly stupid little joke to make people laugh a little because this sort of death really affected a few people, and most of the time people did get it and laughed. I wanted to cheer people up a little and it worked and it made me happy that I could make them happy a little bit.
In fact I posted this on Facebook too just to make sure they knew my intentions with the joke, just to make sure no one got mad at me but so far no one has. It was on the same post I found out about his role as Master Xehanort.
Bad jokes aside it's really sad to see someone so important to geek culture die like that, though with the stress of his career he no doubt had living to his 80s is still pretty darn impressive especially since he was a smoker back in the day, I was never into Star Trek but Mr. Spock/Master Xehanort will be greatly missed.
Honestly I get I'm not one for joke making and sometimes some jokes go over my head, but there are times when I'm not being serious at all either.