Nexus Mod Manager is/will be a tool for handling mods from Nexus. There is still a need for something like OBMM/FOMM for Skyrim. You can use OBMM/FOMM along with NMM. You can also hand place mods into the game and still use NMM to launch the game. If you want more than one install of a game IS and Hana from TESA have a tool in the works called MIMI.
No, really, NMM is the replacement for OBMM/FOMM. I'm pretty sure of that.

Not to say that no-one else would want to make their own mod manager, but the nexus mod manager is the 'official' OBMM/FOMM successor, and will do everything that they used to. (Edit: Including installing mods that weren't downloaded from skyrimnexus, obviously.)