I'm quite sure Scrivener has hit the nail on the head regarding keeping the validity of the novels. Remember that for as unpopular as the 4E Realms were to Realmsfans, there were still a lot of people who had campaigns set there and who enjoyed it. WotC is trying to please as many people as possible with the 5E Realms by going with a non-reboot-reboot (which I'm sure will use a liberal dose of Ao ex machina) the outcome of which is supposed to be satisfying to both 4E Realms campaigns as well as old FR fans.So the "current" timeline is going to stay in the 1400's and not revert back to the 1300's?
Thats a bummer, I really want the awesome Khelben alive again, and Halaster as well, roaming the halls of his sinister dungeon and playing with his magical cheesboard. For Piergeiron to be the Open Lord of Waterdeep, for Randal Morn as the lord of Daggerdale, and a slew of etceteras.
WotC has not yet revealed any details about its product plans for 2015, but it's highly likely we'll see a Forgotten Realms Campaign Setting next year. Given the "edition-to-end-all-editions" strategy of 5E, it's not a stretch to imagine that the 5E Realms will include notes about how to stage a FR campaign set during any one of the periods (read: editions) during the Era of Upheavals.