I personally think James will, if anybody, be the first to call it. The other guys can adjust, e.g. Jordan could start using a stool behind him like so many other keyboard players. The vocals are the ones that you can't work around.
JLB already has to a degree, with the band tuning down and modifying melodies.
I do agree it's much harder for the vocalist to get away with these things though, being so upfront and prominent, and it's also the most important impression on the audience. Most people won't notice if the guitarist is slowing down a bit and fumbling occasionally, but if the singer isn't hitting the notes, it affects the whole show.
Back to the point of discussion though, I don't see anyone leaving the band in the near future. To me that's just bored housewife prog fan talk.