Gnome should ship with Wayland considered as stable with 3.14, and (as far as I know), there's no plain to ship KDE on Wayland before KDE5. XWayland still need works, and without it no distro will ship Wayland. The proprietary drivers still need to come out (Nvidia might be at work on them already, but for all we know it might still be just some drawing on a blackboard - and let's not forget about AMD, that will probably take quite a bit of time).
Also "normal" distro (Mint, openSUSE, Fedora...) will probably take their time as well to ensure that everything is working. I'd expect to see some kind of experimental preview, then a version with support to both (but with the default still being X) and then a version with Wayland (and an X failback).
Probably I'm just being negative here, and if everything happens faster than how I think it will, then great! Also, probably just a generic "years" feels too much, my expected timeframe is/was 2-3 years.
See:
* http://techbase.kde.org/Schedules/Plasma/2014.6_Release_Sche...
* http://blog.martin-graesslin.com/blog/2014/03/kde5-and-wayla...
There are commits [1] on the Chrome tree designed to get Chrome working on Wayland, but for those commits to reach significant numbers of users will require the cooperation or at least the "non-interference" of the employer of most of the Chrome devs -- which is at this time an unknown.
Firefox Bugzilla bug: https://bugzilla.mozilla.org/show_bug.cgi?id=627699
You can install a build on Fedora via this copr (like a PPA for Fedora): http://copr.fedoraproject.org/coprs/stransky/FirefoxGtk3/