Most contributions are required to assign copyright to the FSF, so it's not actually particularly open.
If the FSF is the sole copyright owner they're free to relicense it however they please, if no one else has any controlling interest of the copyright, the GPL doesn't restrict you from relicensing something you're the sole owner of (and it's doubtful there's a legal mechanism to give away rights to something you continue to own)
Again, the FSF under Stallman isn't about freedom it's about control.
If the FSF is the sole copyright owner they're free to relicense it however they please, if no one else has any controlling interest of the copyright, the GPL doesn't restrict you from relicensing something you're the sole owner of (and it's doubtful there's a legal mechanism to give away rights to something you continue to own)
Again, the FSF under Stallman isn't about freedom it's about control.