Honestly you will be able to run todays game in 1024x768 very easily.YES some game required bigger cards( exemple doom 3,far cry) but i was still able to play these games with my 9800 pro evehrything at very high, beside some little options tone down.
In 2006, when quake 4 will come out, yes i think the 9800xt will have problem running it in very high detail, but it will still be playable like medium to high settings.
People todays are able to run doom 3 medium settings/800x600 with a simple ti 4200(release like 2 years ago).In a year with the 9800xt youll be able to play some games the same way people play doom3 with their ti cards,and some games will run very ok.
Its simple, your moving from a year of generation if you decide to upgrade.In one year im sure youll be able to get 100 buck for your 9800xt, when the price of the 6800gt will drop by half easily.
Me i like to be up to date, and because i love playing widescreen, i decide to change card.But if your someone always playing in 1024, using no AA and little AF, then upgrading doesnt really worth it for now.Those new cards are made if you love to play in high resolution.Some people dont mind playing 800x600, some people can't live playing with anything less than 1600x1200.
You 9800xt can hold you up for another good 2 years imo, but i can garantee you that in 2 years, quake 4 wont run in very high detail on your 9800xt
BUT $200 buck for your xt now, and if you got the spare cash to get a 6800gt, yeahs its a good move.Dont get a x800pro tho.Its only 12 pipelines and do not support shader 3.0, the x800 pro really feel like an overclocked 9800xt, iv got a buddy who bought it when it came out, and god he regret it.
Your move depend of the kind of pc gamer you are.
And jeshhh you got a 256meg card, thats even better