It wont make F18. But my current understanding is that a version of Unity can make it into Fedora without patches, the tradeoff being that some functionality will not work.
There has been work upstream in recent versions of Unity to close the gap with stock gnome. It should be usable without patches. I'll find out how usable as I work my way up the the dependency chain and get the necessary dependencies in Fedora.
But unless someone else steps up to drives the effort to get Unity and its specialized lib stack through fedora's review process its going to be awhile before I can find the time to put a coherent set of packages together that have the ability to pass review. I'm working on it, but my travel schedule makes it slow going. I'm still willing to review packages if other people beat me to putting packages into the submission que. At the rate I'm going F18 update is possible, but not at release time.