Hearing that they plan to release new content player options to fit with their storylines (or new storylines to go with their player options) I can not help but feel sad that Tyranny of Dragons got this treatment. Does this mean they would have to do Tyranny of Dragons 2 or another dragon plot if they wanted to do a draconomicon or a draconic player options book? I know it would be silly to expect them to do a splat book in the middle of them releasing the core rulebooks but I can not help but wonder what we would have got if they gave Tyranny of Dragons the same treatment they where planning for other storylines and being the dragon fanatic I am also sort of wished we had got it.
Well, they ARE giving stats for Tiamat and showing some dragon masks. So there's that.
No feats or subclasses, sure. But better than nothing!
I plan on using a couple of book from 3.5 as inspiration for our Tyranny campaign: Dragon Magic (ideas for spells) and Races of Dragon (ideas for equipment). I'm also gonna look at the Draconomicon (for 2e, 3e, and 4e).
Still haven't gotten my hands on Rise of Tiamat. I was hoping to snatch it early, get some games started, but everybody's been busy. Definately on my to-do list 
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I really wish they made each book a heavy mix of both new player content and a quest. I like buying quests, but if it is just a quest, and I don't think I will have time to run that quest any time soon, I usually avoid the purchase. On the other hand, new player content, which I can always offer to a group I am DMing for, almost always interests me enough to make a purchase. As a result, while I really want the books from the Tyranny product line, I haven't been able to convince myself to purchase them as of yet...
I think that is one thing the WFRPG 3e product line did really well. Every purchase had a mix of all types of content. As a result, I own ALL of the quests that product line released. That is something I cannot say is true for any D&D product line to date.