There need to be more details included to answer that one. Even then, I don't think many (or any?) on this forum can answer that 100% truthfully and in its entirety. Regardless, because it is a broken arm, he will not be staying there to train.
Is he a PLC (I'd ask OCC too but they are still inprocessing) candidate? A Marine Option NROTC midshipman? I'm guessing the latter since you mentioned a scholarship.
If he's a PLC/OCC candidate he will have to heal up, reapply, return and try again. If he makes it to commissioning, he will become a Marine. If he's an NROTC midshipman, he will already have a scholarship to attend the 6-week Bulldog course. An injury happened to a friend of mine who was with the Bulldog program. He was allowed to return the following summer and commission afterwards.
With NROTC, I'm not sure of the official NPQ process so I won't comment any further on whether or not he will retain or lose the scholarship in this case. Good luck and a speedy recovery to him.