Anyone could sue any Linux distribution for infringement, especially one of the thousand+ kernel developers, present or past.
Who has the authority to "tolerate" a GPL violation?
It's not like Alan or Linus can simply go ahead and say "oh, ignore the GPL, it doesn't matter anyway" as a sign of good will.
The real meat here is that Nvidia is not really running a risk here, because they do not distribute infringing code. What they want is the distributions to break the GPL by shipping their software. Nobody could legally ship such drivers anyway!