Not the death of FireWire. If bandwidth alone were enough to cause a device protocol to die, PATA might have dwindled away much, much, much sooner as SCSI was around to allow for significantly faster connections with more than two devices. (And yet, PATA and SCSI still "live on".)
Seeing pre-built computers ship with fewer and fewer FireWire ports is not a sign of FireWire going away, but rather of manufacturers cutting costs. Since FireWire devices can daisy chain (you can connect one FireWire device to another FireWire device to another FireWire device up to 63 times), only one FireWire port is needed. Of course, if you really do have several FireWire devices, having multiple ports can save you some device juggling later as you need to add, remove, or move a FireWire device. Personally, I miss having two FireWire ports as standard on my Apple laptop choices. But, if you only have one FireWire port, you can still connect dozens of FireWire devices without adding a hub.
USB devices do not daisy chain. That is, you do not connect one USB device to another USB device to another USB device. But rather, they branch our from the motherboard or a USB hub and then stop there. So, the more USB ports on your computer, the better. If you only have one USB port, you can only connect one USB device unless you add a hub.
USB 3 is indeed fast! Especially compared to USB 1.1, USB 2.0 and even to FireWire400 and FireWire800 And thank goodness for it.
Or course, FireWire 1600 and FireWire 3200 are coming. And you might not even notice if you're just looking at the connector as it's the same as FireWire 800.
Happy device juggling!