A specialist lawyer paid to investigate the subject and write their legal opinion says GPLv2 can’t be revoked (section 7.4 GPLv2 Irrevocability): https://copyleft.org/guide/comprehensive-gpl-guidech8.html#x...

Of course, many other non-specialists have contrary opinions. If you have a link to a legal opinion to the contrary (by a lawyer skilled in the relevant areas), could you please share it?

Do you have any reliable sources for that being the case? Everything I've read, pretty much ever, about the GPLv2 indicates that the version of code released under the GPLv2 is forever available under the GPLv2. You can change the license, but people are always free to use the last version that was released under GPLv2.

So any Linux kernel contributor in the last 30 years can pull their license and force an immediate "emergency rewrite" of everything they've contributed? Since other Linux developers would no longer have a license to use it?

That seems unlikely, or somebody would do it just for the laughs. (I certainly would)