The availability and acceptance of an audio interface (aka "sound cards", which is really a misnomer) is an appreciable facet of Ubuntu Studio with regards to audio performance and usage. The availability of Apple's Thunderbolt and USB 3.0 presents an interesting situtation when considering which device will become the prevelant interface, and therefore effect Ubuntu Studio's future development.
Historically SpeakingApple's previous "high speed I/O technology", Firewire, has provided better I/O speeds than USB. Yes, USB 2.0 theoretically provided faster speeds than Firewire 400, but it did't seem to provide it in practice. Also, Firewire 800 trumped it by providing 800 Mbps vs. USB 2.0's (theoretical) 480 Mbps.
Firewire's acceptance on laptops was also a compelling feature for this audio interface. USB 2.0 has also been available on laptops as well.
The result is that both audio interfaces were used and Ubuntu Studio strove to support both "out of the box".
As a footnote, I should add that USB 1.0 devices' (incredibly) low price resulted in their commonplace usage for certain niches. The frustration resulting from their underwhelming 1.5 Mbps speeds was also commonplace.
Looking ForwardIn some quarters, Firewire has been declared dead and the result seems to be a decreasing rate of available Firewire devices. I do not think that Firewire devices will be the "audio interface of tomorrow".
Thunderbolt offers monstrous performance but simply isn't readily available for PCs at this point. The available cables are equally monstrously prices. Furthermore, devices are not really available at this point either. It would be hard to suggest that Thunderbolt will be the "audio interface of tomorrow" either.
USB 3.0 is already prevalently in PC desktops and laptops. USB 3.0 cables do not seem prohibitively expensive. It seems that only a handful of USB 3.0 compatible devices, which actually use the 2.0 protocol, are available. In good faith, I would not posit that USB 3.0 will become the "audio interface of tomorrow" as well.
The Calculus of Change ItselfHowever, if we remove some variables I think we can logically predict where it might go, although I concede that acceptance isn't necessarily based on logic but rather timing or bias at times.
For the argument, let's accept that Thunderbolt and USB 3.0 are equally available on Mac and PC. Additionally, let's accept that Thunderbolt and USB 3.0 devices are equally available.
Removing these from consideration, we are left with price and performance.
Speculating on prices (since the devices are not prevalently available), I would suggest that Thunderbolt prices will be higher than USB 3.0 devices. Obviously I don't know how much, but I wouldn't be surprised if Thunderbolt devices were priced 150% compared to USB 3.0 devices. I accept that there is a high percentage that I am wrong on the exact percentage, but I would wager that I will be right in concept.
For performance, Thunderbolt provides 10 Gbps(!) speeds while USB 3.0 provides 5 Gbps. However, I believe USB 3.0's 5 Gbps will provide excessive throughput for most audio needs. This may be an inflection point where the technology available has eclipsed the need. I believe an analogous situation is occurring with desktop/laptop computer and phones.