It is astral plane, but astral sea sounds more "romantic".
Maybe the crystal spheres are totally closed for safety reasons, and in the Wildspace is happening an alien apocalypse by fault of unwellcome visitors.
I wonder about why the vodoni empire has could to conquer complete solar system, but not yet our favorite crystal spheres, not even news of these attempts by the natives.
Could there be space zaratans (island-size turttles) in Spelljammers? And their skeletons used as raw material to craft spelljamming helms.
* DC could publish a D&D/Spelljammer version of "Legion of Superheroes". Or Warner could talk with Hasbro for an intercompany crossover. Or Star Trek+Spelljammer, for example a no-canon kid-friendly cartoon parody.
* Slavery is now a taboo in Paizo's Pathfinder. There was slavery trade in Spelljammer. I don't like this type of troubles.
* If Spelljammer is opened in the DM Guild, somebody will publish a ersatz+mash-up version of famous (sci-fi + space-opera) franchises.
* Rom the space knight could appear as an easter egg in some picture, but with a decent redesign.