Save John Watson… from what?

Tonight I watched the death of Mary Watson and I was upset. After surviving a
vengeful former comrade who believed that she had betrayed him, she died saving
Sherlock from being shot by a mere secretary. It was a wasteful needless death
caused almost entirely by Sherlock's need to taunt. And throughout the scene
Mary told him to stop and he ignored her because his inability to truly
understand human emotion. It was actually a cool flashback to that first episode
where Sherlock and Mary met after John had hit him a few times and Sherlock
could not understand why his friend wasn't pleased to see him. This time it cost
a life.

Then came the last few minutes and the message to save John Watson. Save him
from whom? I'm assuming it was the red headed woman on the bus. No idea how Mary
knew about his apparent affair, but maybe there is more to E (after Missy
anytime a character announces themselves as a letter or short name I can't help
think "what's it short for?") and her comment about being a vampire than a
simple joke.

If not then the next best guess is himself. At the end of the episode John
Watson has lost his wife and turned his back on his best friend. Who will help
him put his life back together if the two people who love him the most are not
around? I bet the Molly/Watson ficcers are already working on this.

Good thing is there is only a week until we find out.