I use Ubuntu 17.04. I use ssh with X11 forwarding all the time to display GUI programs running on my server locally on my computer.
Ubuntu 17.10 offers Wayland instead of X11 and I've read through a bunch of posts since 2011 about how this "might" affect X11 forwarded apps. I find many predictions of disaster, and many predictions of network transparency.
Some posts claim that I'll be forced to choose at login between X11 or Wayland. However, I have run X11 servers on both Macintosh and Windows so I don't think this is necessarily an either-or choice. But that's just more guessing. How does this actually work?
Quoting Wayland FAQ
TL;DR is that it "out of scope". Over the years there collected lots of apps and protocols for exactly that kind of job, and there's very little sense in adding this protocol to Wayland.
Worth mentioning that AFAIK nobody have worked on the mentioned hypotetic usage of X.org protocol on top of a Wayland compositor.
I guess you're talking about a bugreport. You won't find one (well, at least not an opened), because it would be closed as NOTABUG.
What's so bad in this? It's not like you lost a functional, there's lots of protocols for that kind of job. Besides, although I don't use X11-forwarding myself, but from what I've read it doesn't work well nowadays for many apps. I vaguely remember, it's because many apps (mainly games and those that heavy on graphics) are using direct rendering and bypass XServer.
You can just stick to X11, I don't see it as a problem. Wayland is still in-development, and X11 won't go anywhere for a very long time. In fact ATM, out of many DEs, Gnome is the single one have Wayland nicely working. You might find it funny, but not even Weston — existing for the sole purpose of being the reference implementation — have it working fully, because it doesn't support the primary selection protocol.
Some development continues in XServer-land too. E.g. just yesterday I have cursory seen some discussion about HDR implementation on #dri-devel channel of Freenode. So it is definitely not anywhere close to get obsoleted.