Anyways, if it's not and it's an actual sequel : no, I'm betting they stick to this formula. Microsoft bought Obsidian, not Bioware. They clearly expect Obsidian games and a return to classics is clearly the directoin they have advertised. It's not the early 2000s anymore.
A decline is still possible, but I don't think they'll change "how it looks".
Microsoft would be insane to have bought Obsidian and have them do projects like PoE with any sizeable amount of staff. They bought them to make an exclusive Oblivion, not indie style games. I guess it's possible a small portion are working on it, but I'd sooner believe they want all hands on deck working on a big Xbox 4 exclusive.