I'm just testing the ElkArte Forum as successor for SMF 2.0 and I'm rather convinced. There are a lot of modification-authors "porting" their modifications from SMF => ElkArte, they need not much work as ElkArte is based on SMF with a lot more embedded features. Since SimpleDesk is also a standalone solution it seems [sic] not difficult to integrate it into ElkArte too.
NB: I'm not a member or affiliate to the ElkArte team - just a completely convinced new user!
There are no plans for me to develop for ElkArte. However there is a fairly similar code base. If ElkArte has compatible APIS to all the old SMF calls, it may work with some manual installs. The new version wrote for SMF 2.1 most likely won't work with ElkArte as it makes use of way more hooks, and ElkArte would have to implant those hooks to function.
That said, SD is open source software. Anyone could fork the project and develop it for ElkArte.