The GeForce 9800 GT will be a single-slot card and it's possible that it features a 55nm G92 GPU:
Nvidia needs this card as Geforce 8800GT clearly loses against Radeon 4850 and it is about time to try to convince people to buy a new card. We heavily suspect that 9800GT comes with the new 55nm chip and Nvidia will do whatever is within its power to get the performance up to level where the new card wins against Radeon 4850. That is why they waited for ATI to make a first move.The GeForce 9500 will be a low-end 55nm part, it should be available by the end of July for $59 or roughly 45-50EUR in Europe.