The mountain is currently covered in scaffolding, so definitely some exterior cosmetic work (paint and whatnot) is happening.
WDW1974 mentioned last year that WDW would get Disneyland's new effects sometime this year. While that plan may have changed, i'd be surprised if it didn't get them. The new effects don't seem complex, difficult or time consuming to install (or even expensive). They honestly look like something that could be installed within a week without even closing the ride (during third shift). Just some digital mapping and/or fiber optics mixed with smoke for the third lift. And the bats flap their wings now (not complicated animatronics by any stretch).
Paris is also getting the effects apparently. I realize both DL and DLP variants of the ride were closed far longer than WDW's, but they're addressing more serious structure/rebuilding/track work.
It would be truly pathetic if they don't add the new effects. Even I think they probably will, and i'm far from a WDW optimist lately...
EDIT- If they're refurbing the mountains for the 50th however, I hope that includes Space Mountain. I won't even ride that anymore as it's gotten so awful. Splash Mountain on the other hand seems to have been kept in decent to good condition for the last several years. It got a huge overhaul a while back, including a new paint job and massive fixes to all the animatronics and such. Still looks pretty darn good overall (I do find an occasional missing or non-working AA, but it seems maintenance related as they return fairly quickly).