Switching licenses to future versions doesn't invalidate previous versions released under GPL.
I'm not a lawyer but I deal with OSS licenses for work and I don't know if there's ever been a case like this, that I can think of anyway.
Their previous versions, still being under the GPL, would require them to release a change to make it usable on desktops. Again, I'm not a lawyer here but there is a lot of case law behind the GPL and I think the user who made the issue could take them to court to force them to make the change if they don't respond in 30 days.