In the extreme short-term, no one. There is always a contingency (for lack of a better term) MEU available for immediate deployment. But, it's what this deployment does down the road 3-9 months that becomes problematic. Unless these guys are back within (roughly) 60-days, you'll see some units get extended in the other theaters of operation.
Past 60-days, and you begin to see a strained Marine Corps strained even further.
These guys and gals were probably in Afghanistan or Iraq a short time ago. This was their rotation back home for maintenance.