The documentation is now officially maintained on the mediawiki site, so your observation is absolutely right. There will be no merge, because the old manual will be just left in the state as it is.
It would be nice if you could copy-paste the sections that are currently empty in the mediawiki version (e.g. several sections in the Armature part). It’s annoying to go to the mediawiki version to look for something just to discover that the section is empty, and then having to go and look in the old manual instead. I usually go directly to the old manual for this reason. Outdated material is better than no material.
Also, the main blender site should be cleaned up because it’s pretty confusing. You can find two different versions of the manual under Infocenter->using blender->Manuals & Books and Download->Documentation respectivly, the latter seems (from the date at the top) to be more up to date. These should be removed or put under “old manuals”, and a link to the mediawiki should be put there instead.