Following up on his earlier post (story) John Carmack made a second post to the thread on Slashdot regarding the future of graphics hardware. This post is much more centered on id's next round of technology, and he confirms that a GeForce 3 will run their new DOOM with all features on at around 30 FPS. Here's his post:

Obviously, any game done with the new Doom engine is going to run slower than a game done with Q3 technology. You can make some of it back up by going to the simpler lighting model and running at a lower resolution, but you just won't be able to hit 60+ fps on a GF2. The low end of our supported platforms will be a GF1 / 64 bit GF2Go / Radeon, and it is expected to chug a bit there, even with everything cut down.

There are several more Q3 engine games in the works that will continue to run great on existing systems, and Doom is still a long ways off in any case, so there will be a lot more upgrades and new systems. We are aiming to have a GF3 run Doom with all features enabled at 30 fps. We expect the high end cards at the time of release to run it at 60+ fps with improved quality. This is an intentionally lower average FPS for the hardware cross section than we targeted for Q3, but still higher than we targeted Q2 and earlier games (before hardware acceleration was prevalent).

In the GLQuake days, light maps were considered an extravagance ("Render the entire screen TWICE? Are you MAD?"), and some unfortunate hardware companies just thought increased performance meant higher resolutions and more triangles instead of more complex pixel operations. Five passes sounds like a lot right now, but it will be just as quaint as dual texturing in the near future. I am quite looking forward to 100+ operations per interaction in future work.