No one has mentioned Apple yet. Unity is Apple's exclusive partner on Vision Pro (for now at least). I can't see Apple being especially thrilled with this.
Open source is indeed unlikely, but there's a very good chance they'd make it free or inexpensive relative to competitors. Plenty of precedent for that in the video editing tools they've bought and turned first-party.
They might not kill off cross-platform support this time, though. Today's Apple maintains true native (not just "port half of the Mac/iOS userland" native) Android and Windows apps.
My pipe dream would be Valve buying unity, being a private company they would not have to deal with pressure from shareholders and they have a good track record with developers and customers.
But they already have their own Source game engine so no point in them doing that.
Microsoft is honestly a better fit given Unity's C# roots and Visual Studio integration. But I find it hard to imagine Microsoft being all that interested in Unity these days. They're already attracting intense antitrust scrutiny vis-a-vis their attempted Activision-Blizzard acquisition.
Given the ubiquity of tech debt in Unity I could see Apple maintaining support for the current C# version for the time being and in the long term, replacing it with a full rewrite based around Swift with a temporary C# compatibility layer to pull the ecosystem through the migration, which wouldn't be everybody's cup of tea but could be interesting.
I'm pretty sure the Blizivison acquisition went through in both the US and EU. Microsoft's not really a huge player in gaming; Xbox and Windows combined are still tiny compared to the other consoles and mobile platforms. And if they use a similar playbook like they did with the acquisition (promising cross platform compatibility for a decade or so), they honestly wouldn't be the worst stewards.
Today's Microsoft is kinda slow and boring, but that's probably the kind of business you want managing a game engine. Reliable, stable to the point of being stale, but reliable. No sudden surprises that give you 3 months to reinvent your last five years of work.
That would be quite something. Perhaps this would also result in Unity's ad business being shuttered or at least sanitized, similar to how Shazam shed all of its third party tracking junk after Apple bought it.
If Apple buys it, it'll quickly head down the path of exclusivity. They'll find some "security" excuse for it that'll be enough for their reality distortion field to do its thing.
Is there such a thing as an Apple exclusive game? I can't imagine a developer would want to cut off like 90% of the market from being able to play their title.
(I think there are a few on Apple Arcade, but I always assumed those were sponsored exclusives?)
There used to be some indie Mac (and later iOS) only game studios like Pangea Software (makers of Nanosaur, Bugdom, Otto-Matic, and Enigmo among others) but I'm not sure how many of those are still around.
As far as bigger studios go, Bungie was a Mac studio until Microsoft scooped them up to turn Halo Xbox-exclusive instead.
How could that work? Even the M2 Ultra isn't nearly as powerful an actual desktop GPU, much less workstation or data center cards. And devs will need to be able to test on Windows machines.