There is a reoccuring pattern from one generation of video cards to another at least when gaming in 1024x768 or 1280x1024 resolutions, which makes the future of ATI video cards somewhat predictable. Generally, after the release of the card you can play the newest graphically demanding games smoothly (at least 20-30 frames per second) at high visual settings during the first year, at medium settings during the second year and at low settings during the third year. During the fourth year smooth gameplay in newest technically demanding games may be impossible even when using very low graphical settings or the card might not be able to run some of the new games at all.
Approximate History and Prognosis:
* Radeon 8500 was released in 2002 and met its end in 2006 in the hands of games that had 128mb/SM 2.0/DX9 cards as the minimum requirement. Radeon 8500 cannot run those games at all because it has neither 128mb RAM nor SM 2.0/DirectX 9.0. In 2004 the card struggled when running Far Cry. In 2005-2006 it couldn't run at all such games as CoC: DCotE and TES4: Oblivion.
* Radeon 9700/9800 appeared in 2003. It was the minimum for many demanding games of 2005-2006 and it will finally reach the end of the line this year. For example, the current official minimum requirements for Crysis mention Geforce 6200 and Radeon X1300. These happen to be the weakest cards with full DirectX 9.0c support. It seems that Radeon 9700/9800 won't be able to run Crysis at all because they are DirectX 9.0a cards. In 2006 these cards struggled when running TES 4: Oblivion and some other games even on low visual settings.
* Radeon X850 was released in 2004 and might last till 2008. The critical limit of the card will be its SM 2.0 / DX 9.0b. In 2008 SM 3.0 / DX 9.0c will most likely become the new minimum requirement and SM 4.0 the recommended requirement for new Top 10 PC blockbuster games because making a path to SM 2.0 might not be feasible any more with DX10 games released. It is possible that even in 2007 some of the most amazing games will be somewhat ahead of their time and might not run on X850 because of the same problem. In other words, some games that will take out Radeon 9700/9800 might also take out X800/X850 out of the race.
* Radeon X1800/X1900 XT(X) should last till 2009 judging on the experience with the previous generations of Radeon cards. In 2009 it will be struggling when running new graphically demanding games and some of the new games might not like the R580 cards at all due to the lack of SM 4.0 / SM 5.0 and DirectX 10 / DirectX 10.1 support.
* Radeon X2800 XT(X) will probably last till 2010 or perhaps even 2011. I suspect that Radeon X2800 XT(X) might have a slightly similar fate as Radeon 9700/9800 because these cards will represent the first generation of cards designed for a major new version of DirectX. It is unlikely that X2800 XT(X) will be brought down by games released in 2010 because of some critical properties like insufficient Shader Model, DirectX capabilities or amount of RAM. However, the most demanding PC games of 2010 might be designed to play smoothly on medium or high settings on video cards that have GDDR5 @ around 5000 mhz and SM 5.0 / DirectX 10.1 support. Radeon 2800 XT(X) will have its GDDR4 RAM "only" at around 2000-2600 mhz.
* R700/X3800XT(X)? (55-65nm, SM 5.0, DirectX 10.1) should be released in 2008-2009 to compete with nVIDIA's G100.
Approximate History and Prognosis:
* Radeon 8500 was released in 2002 and met its end in 2006 in the hands of games that had 128mb/SM 2.0/DX9 cards as the minimum requirement. Radeon 8500 cannot run those games at all because it has neither 128mb RAM nor SM 2.0/DirectX 9.0. In 2004 the card struggled when running Far Cry. In 2005-2006 it couldn't run at all such games as CoC: DCotE and TES4: Oblivion.
* Radeon 9700/9800 appeared in 2003. It was the minimum for many demanding games of 2005-2006 and it will finally reach the end of the line this year. For example, the current official minimum requirements for Crysis mention Geforce 6200 and Radeon X1300. These happen to be the weakest cards with full DirectX 9.0c support. It seems that Radeon 9700/9800 won't be able to run Crysis at all because they are DirectX 9.0a cards. In 2006 these cards struggled when running TES 4: Oblivion and some other games even on low visual settings.
* Radeon X850 was released in 2004 and might last till 2008. The critical limit of the card will be its SM 2.0 / DX 9.0b. In 2008 SM 3.0 / DX 9.0c will most likely become the new minimum requirement and SM 4.0 the recommended requirement for new Top 10 PC blockbuster games because making a path to SM 2.0 might not be feasible any more with DX10 games released. It is possible that even in 2007 some of the most amazing games will be somewhat ahead of their time and might not run on X850 because of the same problem. In other words, some games that will take out Radeon 9700/9800 might also take out X800/X850 out of the race.
* Radeon X1800/X1900 XT(X) should last till 2009 judging on the experience with the previous generations of Radeon cards. In 2009 it will be struggling when running new graphically demanding games and some of the new games might not like the R580 cards at all due to the lack of SM 4.0 / SM 5.0 and DirectX 10 / DirectX 10.1 support.
* Radeon X2800 XT(X) will probably last till 2010 or perhaps even 2011. I suspect that Radeon X2800 XT(X) might have a slightly similar fate as Radeon 9700/9800 because these cards will represent the first generation of cards designed for a major new version of DirectX. It is unlikely that X2800 XT(X) will be brought down by games released in 2010 because of some critical properties like insufficient Shader Model, DirectX capabilities or amount of RAM. However, the most demanding PC games of 2010 might be designed to play smoothly on medium or high settings on video cards that have GDDR5 @ around 5000 mhz and SM 5.0 / DirectX 10.1 support. Radeon 2800 XT(X) will have its GDDR4 RAM "only" at around 2000-2600 mhz.
* R700/X3800XT(X)? (55-65nm, SM 5.0, DirectX 10.1) should be released in 2008-2009 to compete with nVIDIA's G100.