I didn't really think it would be a replacement for USB, Firewire and video (HDMI, DisplayPort, DVI).
Essentially Intel is hoping that copper cables are nearing their peak transfer rates and won't be useful in 5-10 years for high throughput data. Normal rotational harddrives today can read at rates up to 100 mbps, and ssds can do 355. If speeds keep doubling USB 3.0 will be saturated in less than 4.5 years for hdd and 1.5 years for ssd. It took 8 years to release usb 3.0 after the release of 2.0.
The more interesting question is how this will affect the market for thumb drives and cell phone charging. Especially interesting is the question of power at all. If you read the wikipedia article on the subject there is some thought to bundling Light Peak with USB 3.0, or atleast it's power supply standards.