I'm obviously not overestimating anything. Stallman has the power to create legally incompatiple versions of Linux, that could require Linux vendors to invest significantly more dollars to provide updates to Linux in the future. You can keep trying to close your eyes and wish it all away, but with 0 of the ~5,000 applications currently controlled by Stallman breaking with him over GPL3, looks like the kernel guys might be one of just a few if not the only one that refuses to convert.
So does Bill Gates, Steve Jobbs, Darl McBride, Myself, You, and Bill the Janitor. The problem for this whole group is because all key pieces ofa Linux Distro like RedHat are out there in a compatible format those versions can continue to exist. If Stallman was to say put the gcc compiler under a license that says 'this can not be used with gplv2 software' he cant unrelease the versions that are themselves under gplv2. He only has power if nobody has the will and resources to maintain that version themselves, unfortunately for him IBM, RedHat, HP, Novell, and thousands of volunteers will do what needs to be done to keep Linux healthy.
No he can't. He's not the copyright holder, so he cannot change the license it is distributed under.