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.
