I don't think security concerns are a red herring. I think the computer industry is starting to realize that consumers cannot be expected to know who to trust, and it is up to the computer industry to start building in genuine security layers. Apple is a company that has only started to get serious about security in the last year or so - before that, they were able to get away with the phony pretense that their computers were "more secure" just due to the fact they were not targeted.
Things like expresscard and Firewire came from a pre-security era - security was hardly considered at the time.
I am not convinced that Thunderbolt will succeed. I did a search for a Thunderbolt PCI/PCIe card on ebay and couldn't see anything - not a good sign. Is Intel licensing the rights to AMD, Marvell or anyone else to make chipsets or is this an Intel-only technology? If it is Intel-only, it will have a short life until a USB 4.0 or a new generation fast Ethernet comes along.
Intel may love the idea for a serial bus expansion interface, but I think the computer and operating system industry will realize they cannot go that way, no matter how much techies like us like the idea.
The big change is peripherals are now running full-blown linux-based operating systems full of third party software stacks. Even if you trust Canon, Nikon, Sony, etc, you do not know who wrote 90% of the software running on their devices. In many cases, the manufacturer probably does not know either. Companies like Sony have shown many times that they are clueless about security.
There will be a need for an interface that can stream real time 1080P and 4K video from consumer devices. I don't think the long term interface exists yet, but it will come. Expresscard, Firewire and Thunderbolt will all disappear into forgotten history. We will still have RS232 though and USB.
In the mean time, the Pro Audio and Video industry will still probably have to offer dedicated PC cards as an option for maximum multi-channel low-latency performance to their audio/video capture/streaming boxes.
Richard.