In case some haven't noticed, the last couple threads have been merged into the existing one as none have provided any new info.
There is nothing for SM to do yet as there is no release yet. We'll know more once it's out.
Right now it sounds like it is a new engine, based on the L4D2 engine, but with some of the Portal 2 tech added. If it is a new engine, that means a new sdk (separate from l4d2 or source2009/orangebox-valve), and new MM:S and SM binaries. The good news is that if they release the full sdk for it as they claim they'll do, full engine headers will be available and a port should not be difficult.
Again, most of this is speculation as it's not out yet and very little official info is available. Have patience
