I'm actually fairly sure that none of the major settings outside of the Realms and maybe Greyhawk will get more than a passing mention. Eberron specifically has a call out in Fizban's Treasury that it's not a fragment of the "First World" and is located in the "depths of the Ethereal" and sequestered away from the influences of the gods and other cosmic powers. I think they're setting up that the crystal spheres hold a lot of worlds, but not all worlds are in a crystal sphere and perhaps that the worlds in the crystal spheres are also all the fragments of the "First World". (Of course my mind has been corrupted by Grant Morrison comics - the whole "First World" stuff and Eberron not being connected to it feel like a very meta discussion of the split between 2e and 3e and/or TSR/WotC ownership of D&D done as a myth. So I'm possibly reading too much into it).
Mystaraspace isn't a thing in Spelljammer traditionally - Mystara was never in a crystal sphere and had its own cosmology. The stuff on the wiki about Mystaraspace is taking all of the information from the old Immortals Set, the Princess Ark articles, and the space articles from Dragon that Bruce Heard wrote and backfitting them into Spelljammer. Mystara hasn't been mentioned in a 5e product IIRC since Saltmarsh - and I don't expect this to break that mold. I strongly suspect that Mystara's links to real-world cultures are a bit too hot for Wizards to want to touch right now. I could be wrong, but given that it was mentioned in a few products and then has been conspicuously absent since, I'm don't think I am. (I'm a big fan of Mystara but I get it.)
I'm betting that the bulk of what we get will be Realmspace (Minsc and Boo ties alone mean it will get front and center treatment) , along with the clusters you mention and then some new ones or some of the lesser spheres reimagined into bigger settings. I expect to get at least as much variation from the original Spelljammer stuff in this regard as VGtR had for Ravenloft's domains. Possibly more because there's actually less Spelljammer material to work with - Ravenloft had a huge product line compared to Spelljammer.
Also I suspect that the setting from the 3e "Shadow of the Spider Moon" Spelljammer conversion could make it in too. I don't see it on the wiki, but it was a fun little setting and could be a springboard for a dev to do something with.