Don't know if they need any big projects. Just keep filling up the holes still left in the current "projects", as has already been mentioned above.
- A small-ish ultra wide angle prime for 35mm is missing, a "DA15 for FF" if you like. The DFA20/4 that Norm requests would be very hard to resist.
- A DFA200/4 WR Macro would be great.
- A full sized 645 might be a good idea, although it wouldn't be for me.
Other than that I can only think of incremental improvements:
- Keep the APS-C line alive with a new flagship model (my K-3 has lots of life left still, though)
- Eventually a successor to the K-1 (and 645Z)
- Keep the lenses coming, whichever they may be
- Some updated TCs could be nice
- Also time for a new GR, I think
...so lots of things to do without introducing any "Next Big Project"