I also don't think X will come to an end so quickly.
Anyhow searching for info on the internet, it looks like Mir provides an X stack on top of
it so that X application can continue to run. As long as that is available, we should be
able to get along.
If one day X support is completely dropped, then we will have a problem and we will have
to consider the best way forward.
Cheers
Michele