Nah, the 256mb 9800pro was around before the 9800XT came out.
I know this for sure, because I was involved in a legal wrangle with a particular company around that time.
It was between the time that the XT was announced, and when it was released. The 256mb 9800pro was mistakenly advertised by this company at £130 (when it was retailing for around £300 at the time, being the top end model). A few hundred people placed orders overnight at the time, and the company resisted, saying that the price was clearly a mistake. In the end though, they had also advertised the product at this price in an edition of PC zone, and so had to admit that the price wasn't 'clearly' wrong, as it wasn't spotted before the ad was placed. In the end, we all got 128mb versions of the card at £130 instead (which was still a bargin)