Given that the D23 panel had a little dedicated Space Mountain conversation for Paris and Tokyo, and no mention was made of MK's, perhaps the scope of the alleged imminent redo is not going to be as all-encompassing as some had thought?
ETA: The word percolating over on Magic is that Disney wants to see the reception to Tokyo's complete redo before deciding between going with totally new ride, or just a rebuilding what's already in there.
But who knows.