Forced conversions are the lifeblood of the hardware industry, and as far as I know, pretty big in the software market too.
I'm running an AGP XFX Geforce 6800GT in my rig right now, so it's not like they don't make AGP cards anymore. Though, if you're an ATI person this is the last you'll see of AGP ATi cards. Nvidia's gonna run one more generation, then it's switch over or don't upgrade.
As it stands it's pretty pointless, modern graphics card just don't need the bandwidth. AGP4X is barely being used, much less 8x or PCIe16. But intel's been pushing the switch, so others end up following. The extra electrical power over the PCIe bus helps though, at least reducing the number of molex connectors in your machine.
Might be nice if the 1x PCIe slots on modern machines actually had some hardware that used em though. It's supposed to replaced AGP and PCI, but so far it's only managing to replace AGP. Most of the actual use of PCIe replacing PCI I've heard of was limited to on-board gigabit ethernet adapters running over the PCIe bus.
So far, PCIe is a serving as a non-PCI replacement and as a glorified AGP64x when we weren't using the bandwidth of AGP8x. SLI is nice - but, goes without saying that people running SLI aren't forced into anything. They have the money to spend and they like spending it.
SATA's already here, doing well though it's still pretty unneccessary. RAID options are nice, and the thinner cords don't disrupt airflow like PATA did. Needing a damned floppy drive to install WinXP isn't so great. AMD's mananging to keep good old DDR around, and since switching over to DDR2 yields essentially no performance benefits as of yet and would require a redesign of the onboard mem controller, DDR's likely to stick around. Dunno much about DDR3, but you'll likely see it on intel first.
As for BTX, I'm not sure what to expect that. Mostly a patch on hot running intel chips. AFAIK, AMD chips can't actually use the form factor, and intel chips won't be able to integrate memory controllers if they're using the form factor. Something about trace length being too far for the ram placement.
