I'm sure it could be a great adventure, but I'm really not a fan of adventure paths or meta plots in settings. I currently like D&D Next and the Forgotten Realms. I'm even been planning out using the FR in a 5e campaign soon, but this announcement gives me pause. Didn't they listen to what the fans have been saying? I'm pretty sure the majority were not saying - "you know what the realms need more of: meta plots that change everything".
Maybe I'm better off just homebrewing my setting so that wotc doesn't pull the rug out from under me every few months.
I think WotC has actually been keeping this in mind. Take a look at
Murder in Baldur's Gate or
Legacy of the Crystal Shard. Both of these adventures (available in stores) came with a booklet providing extensive information on the city/region/environs. Even if you don't run the adventure, there is a lot of value there. If I were running a city adventure I would break out Murder in Baldur's Gate and mine it for ideas, regardless of where the city was, because it's an excellent resource for ideas. Even the later adventures, such as
Scourge of the Sword Coast (available on DnDClassics), have some very useful information for anyone running an adventure in Daggerford (more background is found in
Ghosts of Dragonspear Castle and also in the older
Under Ilefarn).
So, sure. If you don't like pre-published adventures or adventure paths, those products will be of less use for you. But, they do have elements that may make them still worth considering. WotC is currently creating adventures that tie in very richly to the FR setting, providing a wealth of information useful to DMs.
As for pulling the rug, you are the gatekeeper. Take the Spellplague. An adventure such as
Lost Crown of Neverwinter can still be great inspiration. Lost Crown isn't lore heavy, in part because it came out to support the excellent depth in the 4E Neverwinter setting book. But, it has a pretty fun tragic tale about a spellplagued NPC and their influence in the city. It also deals with a part of the city where they try to cure those afflicted by the Spellplague. That tale can easily be converted from 'Spellplague' to any kind of magical illness or curse and still be a compelling tale. You don't have to adopt WotC's Spellplague timeline to make use of this.
Tyranny of Dragons will be the same way. Tiamat may be somewhere at the end of this, from what we hear of it, but any tale with dragons creating an alliance and weaving in the Cult of the Dragon and the Red Wizards sounds like fun. Those are great elements for inspiration in FR, even if you don't use them in their entirety.