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Android will become a locked-down platform in 194 days
(keepandroidopen.org)
This is a most excellent place for technology news and articles.
I think the problem is your second assumption of "will continue releasing sources" is the one to fail.
Hence, a new OEM.
The OEM makes the hardware tho. How does that help if Google stops releasing the Android source code?
If Google goes closed source and nobody sustainably forks Android we can go back to Linux. This should bring tablet (don't care for phones) support to genuine usability rather soon.