Three people today have told me that the conference rate at Hilton Hotel is sold out (rooms are available, but they run about $300/night) and the Wyndam hotel is essentially sold out (only single nights are available) for both the Business Partner Conference and the Developer Summit. So if you want to attend either, you are on your own. Best of luck!
No room at the inn for weary ArcObjects developers
UPDATE: Rooms might be available at the Hilton now. YMMV