It's been over a month since the release in question. Wayland is already updated.
Relevant PR: https://github.com/gentoo/gentoo/pull/2816
dev-libs/weston-2.0.0 was released on 2017-02-25. https://lists.freedesktop.org/archives/wayland-devel/2017-February/033231.html
small update: 1.12.0 is now in the tree, will work on 2.0.0 later.
This was badly needing some love so I have done the bump to 3.0.0 myself. The tests (which no longer require an X display) pass reliably. I fired it up via X11 on my amd64 desktop and using DRM on my ARM box.
Thank you!