I agree here, and I think Icaza is just motivated to make something for himself, because as he explained in the talk, he loves Apple products and APIs.
Swift cross-platform would be a great thing.. I see that The Browser Company is using it for their browser project [0]. It's got a good mix of speed and ergonomics, and Apple seems hell bent on using swift for everything, even at the kernel level (I can't look up sources atm but Sean Parent has said this on ADSP podcast, and you can see the various talks from C++ conferences about swift as a "successor language"). You're right though, Swift is always going to be beholden to Apples whims, just like C# and Microsoft. I feel like Rust has the best shot at being "the cross-platform language to rule them all", but it has a long way to go in terms of being as ergonomic as Swift or C#.
CAPCOM has their own engine based on a fork from .NET Core, used it on Devil May Cry for the PlayStation 5.
Good luck getting similar adoption for Swift outside Apple platforms, specially game consoles.
If not C# alongside C++, studios would rather use Rust not Swift, e.g. Embark and Activision.
Metal has now C++ bindings, as Apple had to cede Objective-C and Swift bindings weren't being welcomed by major studios.
I like Swift, however I don't see SwiftGodot going anywhere outside iDevices.
That isn't bad if that is the goal though, plenty of companies are doing quite well being single platform.