Since the question has been somewhat dodged and not really answered, I would like to re-ask it: is there an update planned for 1.2.4, or are we stuck at 1.2.3?
It's not much of an update, but the unavailability of the earlier server jars presents an annoyance if you happened to miss the window to download it. MLMP has recently been updated to 1.2.4. I can't imagine there are too many wrenches porting from 1.2.3->1.2.4. Still, would be good to know if it's planned or not so people don't keep asking. Then again, there's no news on Buildcraft or Redpower being updated, either.
I've been following buildcraft dev for a few days and found that they have started porting to 1.2.4. Time will tell.