They have co-existed for the last five years or so, and I don't see it changing any time soon. USB's functionality is centered around input devices like keyboards and mice, and of course there are some mass-storage USB devices. FireWire's focus is on digital video and larger mass-storage devices like external hard drives. To my recollection, none of the original proponents of FireWire ever envisioned it as a direct competitor to USB. In some areas they do rub elbows, so to speak. As it stands now, USB and FireWire have gotten along nicely, and there's no reason not to have both interfaces in a PC.
they both have their uses usb for things that dont need massive bandwidth firewire for the htings that do, but i think usb should be around, it wouldnt make sense plugging mice and printers into firewire ports lol