and getting leapfrogged when the cheaper technology caught up.

Apple used to be exclusively SCSI devices, IDE caught up and SCSI lost out. Firewire vs. USB is another. And I'm betting we can come up with a dozen more.

For a technology to be replaced the new technology needs to solve the shortcomings of the old technology. USB Mice/Keyboards/Printers/External Hard Drives/MP3 Players are all light years better than the old PS/2, Serial, Parallell and a few more interfaces I'm forgetting devices.

For thunderbolt to succeed, somebody will need to come up with a killer consumer application of the technology. USB 2.0 drives are good enough. Mice, keyboards, external DVD's are good enough. We really don't need to replace them. If all you can say about the thunderbolt is that it's faster than USB, there only a limited market for that. It won't be enough to penetrate the consumer market and unseat USB.