Yep 8x is supposed to be out with the next chipsets. I have read two different things on it so far one says that it is backwards compatable to 4x and the other says all the way back to 1x. Malaki also said in another post that it was supposed to be back to 1x. Unfortunately I can't remember what sites those articles were on that I read. I'll try to come up with them later on today or tonight and post them here for you.
I believe Nvidia and ATI's next GPU's will call for agp 8x. Nvidia's will be the eclipse and ATI's the R300 (just codenames as of yet). Probably won't see these cards until Fall 2002 at the VERY earliest.