I always assumed that re-visitation was a standard thing with the Titans, something along the lines of a routine checkup and maintenance. Y' know. Top off the oil reserves, make sure the planetary temperature's humming along, make sure the planetary biodiversity is up to factory specs, check the seals on the NIGHTMARISH ELDRITCH OLD GODS FROM BEYOND SPACE AND TIME, that sort of thing. Basic planetary care.

Rescheduling the visitation then, either means the Titans are getting antsy about Azeroth, or, alternately, they've got other cosmic fish to cosmically fry. Maybe trying to deal with the Burning Legion elsewhere? It does seem like the kind of thing they'd be interested in.

On the other hand, even leaving aside the Old Gods slipping their shackles and getting smacked down for purples, there's been a LOT of crap going down on Azeroth: The Sundering, the Shattering/Cataclysm, something like a dozen alien species coming to inhabit the planet. All that right there might be enough to put us on the list of planets to check up on.

Time will tell, I suppose.