I think Grandgrant won't get invited, which sucks because he's easily the most enjoyable caster imo, I started by hating him a few years back but after watching him on random streams and shit, he's just hilarious and he has some interesting insight in some of the teams and personalities. But he also kinda doesn't fit the TI image too much I feel, so don't know. If he gets invited I'll be happy, even if he ends up only casting pool matches and shit, that's still pretty nice.
LD said he was looking into getting back into dota casting too. Although he said he wouldn't do TI even if he was invited for some reason, because he felt it'd not be respectful of other casters who put in work all year versus him just kinda announcing it at the last moment. I'm not a big fan of LD but I kinda liked him so nice he's coming back.
Also not sure how you can talk about guaranteed casters and not list Tobi, probably forgot, cause I just don't see a TI without Tobi unless he himself declines to go, he's basically the voice of dota2 casting. Plus he makes a good pair with Lacoste or Synderen, both of which might get picked up too.