> If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.
So Linux could've theoretically upgraded to the GPLv3 (or GPLv2+). However, Linus didn't like that idea, and in 2006 edited the COPYING file to say that it was GPLv2-only. If you really wanted to, you could take the 2006 source code and make a GPLv3 fork of Linux.
You certainly theoretically could, but maintaining, updating, and modernizing such a beast would be out of the reach of most people and organizations. 11 years of progress can't be replicated so quickly, especially when you consider you'd need to do it in a clean-room sort of fashion to be entirely aboveboard, which means many people who are already well familiar with the Linux kernel couldn't even work on it.
At any rate, I think your estimate of the timing is off: I found references to the "GPLv2-only" language in the kernel's COPYING file as far back as linux-2.4.0-test8, which was released sometime in 2000, and I didn't really try to go farther back.
He has said from the beginning that the choice of GPL for Linux was a technical one that he thinks produces the best code, and that the GPLv3 offered no technical gains and thus wasn't worth switching to. Presumably if he thought switching to a different license altogether produced better code, he'd do that.
Is not having an opinion on software freedom an ideology? I don't have an opinion on most political questions in, say, Mongolia. Does that give me a particular ideology on whatever political spectrum Mongolia has?