The UBports team published a short Q&A this weekend about their initial Unity 8 plans. In there they comment of Mir/Wayland:
Our short-term plan is to keep Unity 8 and Mir as is. We need to learn how to build these projects into system-image-server through automated means. We will also look into running Mir on top of Wayland as a stop-gap during the Yunit (unity8org) transition to qtWayland (if that happens, their community hasn’t decided yet).So obviously they will stick with Mir for a little while until the project gets off the ground and it won't be an overnight process transitioning from Mir to Wayland, but they do have hopes to do so. The Mir-over-Wayland may also be part of their transition process, which might not be too bad if they can map MirAL to Wayland.
We DO NOT want to be maintaining a display server. By moving to Wayland we get native Libhybris support, meaning we should be able to work directly on the upstream libhybris. Until that is possible, though, we will ensure that our infrastructure can support our OS: We need better updates and some release policy changes: devel (nightly), rc-proposed (weekly), and stable (manual push), details TBD.
Separately, another community fork of Unity 8 is going by the name Yunit. Not many details there yet, but they do appear to be pursuing eventual Wayland for their desktop-focused Unity 8 fork. UBports developers are in contact with Yunit, but so far they are keeping to their separate focuses of UBports being mostly interested in Unity 8 for mobile devices. Yunit is hosted on GitHub.