I don't think Tyranny will have dragons or too much typical fantasy stuff, but I too would welcome a change of scenery for sure, some new IP set in the real world or a good sci-fi, or something that hasn't already been done to death like classic fantasy rpgs.
As for Fallout, Obsidian managed to pull out a great game with NV but it would've been even better if they didn't have to work on that framework, so why not make their own stuff? Now, of course they couldn't make an AAA rpg without a publisher like Bethesda, but who cares? A smaller project may be both more profitable for them and better quality-wise.
True, from the looks of it Tyranny does look a bit different from generic fantasy with dragons. The premise itself is very much different from those just alone, so even though it is fantasy based, there's still freshness to it. Another "generic" fantasy rpg after PoE would be kinda of disappointment when there's so many different settings they could be working on.
Yes, a smaller project can be highly profitable for Obsidian as proved by PoE. If they save up some of those profits, they just might get to make their own "Skyrim" at some point if their recent success continues and they don't just use all that money on crack and whores.