It was never going to be possible for Linux to switch, so it's honestly a bit of a moot point. By 2007, the overwhelming majority of copyrights were not held by Linus and lots of the code was already licensed as GPLv2-only (not to mention that tracking down copyright holders pre-Git would've been basically impossible -- and that's before you start worrying about bankrupt companies or people who've passed away). Switching licenses is incredibly hard, and in my view it was a mistake to make GPL upgrades opt-in (they should've been opt-out as is the case with the Mozilla Public License).
I also broadly disagree with the argument that if the Linux community (or in this case, Linus) is against something then it is not a reasonable thing to put in the GPL. A reminder that the official policy of the Linux Foundation and lead maintainers is to avoid GPL enforcement at all costs[+] -- meaning that by this reasoning, the GPLv2 having any enforcement provisions at all is "too scary".
[+] GregKH has spoken on this quite a few times. I don't disagree with their view that enforcement reduces the chance of recurring contributions (which is what they actually care about), but it does mean that Linux's usage of the GPLv2 is more akin to MIT but with some extra public shaming if a company doesn't provide sources.
The LLVM relicense shows that it is actually possible for a large project with distributed ownership to switch licenses given there is enough motivation to do so. From what I understand as a non-lawyer, situations with this old code where the copyright owners can't be tracked down is undesirable for a number of reasons and they may need to rectify that eventually anyway. (I believe it can be seen as a liability)
> It was never going to be possible for Linux to switch, so it's honestly a bit of a moot point.
It wasn't moot because:
* the FSF apparently attempted to convince Linux devs that the GPLv3 could be compatible with Linus' intended use of GPLv2
* Linus has publicly claimed they were mendacious in his communication with them
That's not a great starting point for adoption of a new license. And while I'm sure there was also plenty of self-serving FUD coming from companies about the GPLv3, this ain't that.
I also broadly disagree with the argument that if the Linux community (or in this case, Linus) is against something then it is not a reasonable thing to put in the GPL. A reminder that the official policy of the Linux Foundation and lead maintainers is to avoid GPL enforcement at all costs[+] -- meaning that by this reasoning, the GPLv2 having any enforcement provisions at all is "too scary".
[+] GregKH has spoken on this quite a few times. I don't disagree with their view that enforcement reduces the chance of recurring contributions (which is what they actually care about), but it does mean that Linux's usage of the GPLv2 is more akin to MIT but with some extra public shaming if a company doesn't provide sources.