I understood it as something of a metaplot thing - though of course, the extent of such things can vary somewhat. For example, if it's just a matter of "Hey, that's the druid from the ruined town in Lost Mine of Phandelver, good on him that he's gone on to bigger and better things." If it's more along the lines of "When major event A happened in adventure B, villain C used the opportunity to set plan D in motion, and that's what adventure E is all about", that's not so cool. One of the major things that turned me off of FR in the past was the metaplot.I thought he was referring to the disparate elements within a single theme - so links between the novels, adventures, MMO content, etc that all come from the same story bible. I could be wrong though.
One big story in 2016? That's even less than the two Adventure Paths per year Mearls was talking about.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.