Mrs. Hudson is basically describing the rest of the season. I guess we should have paid more attention, because her friend that left early was Sherlock and her relationship was like John and Mary's. Wow.
Except...it isn't really, is it? The people who loved him have moved on, John isn't just his anymore. It will never be the same--but this new thing it will be? The man Sherlock can learn to be? Maybe it will be even better.