I've seen what TB can do and it's great. But what I'm saying is that it will be HARD for TB to step into a USB-dominated computer industry and just kill USB altogether from all angles. Will TB be faster than USB 3.0?...in real world use by 90% of the consumers/prosumers out there? Maybe. Maybe not. It's like asking Bluray to come in and just dominate the DVD market...it's been trying and 3+ years BluRay is doing well, but the average Joe understands he needs to re-purchase all this movies as well as purchase a hi-def tv and stereo receiver to take advantage of all the features of Bluray (I love Bluray, by the way). It's time, money, and not everyone sees the value or HAS A NEED for that value.
Will people throw out all their USB devices and twiddle their thumbs waiting for TB devices other than hard drives (cameras, printers, video cams, keyboards, mice, flash keys,)? No. Of course not.
Speed vs. Speed is 1 argument...versatility is another. But again, what I'm really saying is to look around you and ask yourself if the world is just going to dump USB technology for TB? Nope. TB will likely coincide with USB 3.0 just like eSATA and Firewire.
We'll see in a few years where we are.