Right but a 9800GT would be positioned with a lower price than the 4850...(with the GTX/GTX+ priced to match it)
however I'd argue that even though a 9800GT would be capable of running on a single slot cooler much like the 8800GT or 4850, I'd say that none of those cards should be, thus I've got an Accelero S1 on my 8800GT and my 4850 (my 8800GT actually came with a nice 3rd party cooler, but refused to be adjusted to reduce noise).
but there might not be much room for a 9800GT as it is...4850s have the look about them that they could drop in price to trump any 9800GTX let alone a GT, and they have the trump in performance as well, so price/performance is definitely a key there. 9800GTs would have to be somewhere around $129 (maybe more, maybe less) and that is getting into the already very crowed arena of G92 8800s and 9600s as well as the 3800s and soon to be 4600s