When I envision the zombie apocalypse I can't say the return of redundant electronic interfaces from the dead is quite what I have in mind, but nonetheless that is exactly what has happened. While I don't know of anyone who has owned an AGP card since the hay-day of the ATI 9800 series (and nVidia's awful FX range), cards have been knocking around based on more recent chips generally asking ridiculous prices for inferior products. Considering we'll be moving up to PCI Express version 2.0 soon it seems an odd time to pledge support for the last generations technology.
Apparently nVidia and AMD see things differently and want to cash in on lend their support to the apparently large market of users hoping to use the latest graphics hardware with the best of 2003's CPU and motherboard offerings. Admittedly the main demand for this support is cited as LAN centres (clearly not real LAN centres) who supposedly can't afford the upgrade to a PCI Express platform.
For nVidia this means creating a new PCI-E to AGP bridge as the current incarnation, designed for the 7-series, isn't compatible with the 8xxx range, which doesn't surprise us in the least. The new version is going to be designed to work with 8600 and 8400 GPUs and the upcoming G92 chipset. No AGP 8800 Ultra's then - shame.
AMD purportedly already has the infrastructure in place for AGP versions of its 2600 and 2400 cards but is having problems with DX10 and HDMI on the aged interface. These wrinkles should be ironed out by the end of this month according to sources so we should expect to see cards soon after.
We probably don't have to worry about the offerings from either company trying to eat our brains, but you probably can expect a hefty bite out of your wallet for the privilege of owning one. Ah, progress.