To be clear, there is no such plan to migrate from the wiki, but I think (I believe I'm not alone), that some kind of additional, structured documentation available in the form of online/off-line HTML, PDF or some e-book format would be certainly nice, it's de facto standard today in most projects.
IIRC it has been discussed two times already, see the last attempt.
Feel free to refresh that discussion on the development mailing list.
Well, it "just" needs someone dedicated enough to make this happen, in other words it means submitting patches
needs someone dedicated enough to make this happen
my own experience has been, the more time spent within the project, the less time i spend consulting the wiki. cloning master, reading source, looking at commit logs and such, seems like a better investment in the long run.