KDE 4.11 will support Wayland.

The git version of Enlightenment should run natively on Wayland, IIRC, Enlightenment 18 will for sure. KDE SC 4.11 Beta has very basic support for that, but the switch is planned for the versions that base on Qt 5, of course, since that toolkit will have native support in 5.2. Gnome will support it with Gnome 3.10. XFCE and LXDE, AFAIK, currently have no plans to port to Wayland, since they first have to port their applications to GTK 3 or Qt 5.

No Xfce... no deal.

How long will xwayland be supported, though? I depend heavily on ctwm, but also xterm, xv, xli/xloadimage, xpdf and gv. I read that Ubuntu's xmir will be dropped at some point. Will the same happen to xwayland?

You can be pretty sure that as long as Red Hat's customers run X applications neither Xorg nor XWayland will go away. It also may be possible that the maintainers of those projects decide to port their software to Wayland, if it is widely used.

The way I understand the FAQ, there are absolutely no plans to get rid of either X or xwayland:

Until there's FVWM or equiv for it I'll stick to X.

When I do attempt a usage, I will create a virtual machine and check the network usage first. It it as issues, well forget Wayland. I am always ssh into machines and using the "DISPLAY" back to my machine. Without fully backward network display, it is as useful as a window manager as "cat".

Switching away from Xorg to Wayland will benefit the whole system. The Wayland system is much less complex than Xorg (as explained here - http://wayland.freedesktop.org/architecture.html). I dare say that the desktop will use fewer CPU cycles and therefore speed up the system as a whole. Mir certainly has that benefit (albeit from M. Shuttleworth's word only - http://www.markshuttleworth.com/archives/1269).

The problem as far as I see it is, Nvidia are committing to Mir support and not Wayland support. I don't know about AMD. I think they are the same, but I honestly can't remember. What I see for the future is that Nvidia will stop producing Xorg drivers and start only producing Mir drivers. Sure, you can use nouveau drivers, but ultimately I see Mir taking over with Xorg being the backup/legacy choice. Personally, I don't want Mir to 'win' but I think that is what will happen.

I would love to see Wayland in /extra. The only way for it to be taken seriously is for it to be used. And not in Rebecca Black Linux. If it doesn't appear to be used, it will fade into obscurity. Xorg will persevere for some time, but the benefits that a new graphics stack bring more reasons for people to switch.

But all that is my opinion.

There is no official statement that Nvidia provides Mir drivers and I doubt that they will not provide Wayland drivers. Despite the fact that Mir and Wayland drivers are basically the same (both are EGL drivers, only that Wayland needs one extension for the EGL model), that Wayland is agnostic to its driver backend (even software rendering works) there is still the issue that both, Nvidia and AMD, basically don't care at all about consumer Linux, they care about their profitable workstation cards. Support for consumer cards is more or less a simple byproduct of the drivers for the professional cards. Since most professional customers of Nvidia/AMD go for RHEL and SLED (which both will switch to Wayland) it is unlikely that we will not see Wayland drivers from them.

If you also keep in mind that Mir is a one-desktop solution (only developed with Ubuntu's Unity in mind) and not supported at all by any other DE/WM it is also unlikely that Mir will be the winner, it is more likely that Mir and Wayland will coexist, like Xorg and Android's SurfaceFlinger already coexist.

Wayland will be optional for Fedora 20 and default in Fedora 21, at the same time the Gnome/GTK teams will have complete support for Wayland. Kubuntu will switch to Wayland. KDE is already working on Wayland support, basic support is in KDE SC 4.11, complete support is aimed for in the next version (KDE 5 or however they will call it). Enlightenment 18 has basic support, 19 will have complete support. XFCE will support Wayland in the future (according to their mailing list), but they first have to port their DE to GTK 3. MATE will also support Wayland.
None of these have plans for Mir support and besides Ubuntu (the main version) I have seen no statement at all from any other distro that they would use it as default (likely it will land in Arch's AUR at some point, like Unity).

I want to fall in love with an all-new minimalistic window manager, written from scratch for wayland.

I would like to have a port of i3 for Wayland, but my programming knowledge is too basic to do that myself.

I have a weird feeling that neither Wayland or Mir will ever be truly adopted over Xorg. Yes they're nice concepts but in practicality they're about as useful as a screen-door for a submarine in terms of keeping water out. I see Wayland and Mir "features" being backported into Xorg to extend it's capabilities and redraft Xorg somewhat, but as far as Wayland or Mir taking over for Xorg, not possible. Xorg/XFree86 is too widespread, too used, and too ingrained into UNIX, BSD, and Linux to be replaced on such a massive level with brutal efficiency and effectiveness equally on the same level.

XWayland being a compatibility layer kinda hints at what they want to do, but in reality, selling Wayland is going to next to difficult if not impossible to the various kernels and operating systems out their all UNIX-like and based. The problem is going to be getting everyone on board equally: hardware OEMs, software developers, and even distribution maintainers, and more. Unless everyone is on board with Wayland, more than likely it won't happen.

We will see. Most distributions have Wayland already in their repositories and the larger ones already confirmed that they will switch.
About backporting its features, mostly impossible and missing the point, since backporting those features can only be done when you break compatibility, which is, besides its widespread use, the one major point that can be counted as an advantage for X.
I personally appreciate this development, new does not have to be bad, especially when new is done in the way the Wayland developers have done it.

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If done the right way, it could be completely seamless a switch over from X to Wayland, but in order for Wayland to be seamless, it has to have total support in all areas especially desktop environments, drivers, etc.

I wish the Wayland team the best, but I seriously hope they don't rush perfection and end up whipping up some half-butted replacement that only breaks your video.