my two cents...
TB is PCIe. So if you have a form factor that supports cards in slots TB has only one advantage, access to certain audio hardware, e.g. The UAD Apollo family. If you really want to use an Apollo you need TB, and it is not yet supported on Windows.
PCIe bandwidth is overkill for audio! Note I said bandwidth and not throughput...
the CD standard requires approximately 10MByte/sec, or roughly 1,411,200 bits per second.
32 channels of 24 bit audio sampled at 96 kHz requires about 70 MBits/second, or about 8.8 MBytes/second
TB v1 provides 10 Gbits/second, TB v2 provides 20 GBits/sec. So can you fit 70 MBits/second on TB???
But nothing is ever quite that simple. In addition to the maximum bandwidth, one needs to worry about how I/O requests are serviced. Well, with USB2 and Firewire you need to worry about that, and in fact the big benefit of Firewire over USB was how I/O was serviced. From what I've read (I have not dug very deeply) USB2 and especially USB3 now support DMA and high efficiency interrupt handling, so there is no longer a performance difference between a well written (with respect to our requirements) USB driver and a well written Firewire driver is minimal. (This does assume you are not using plain vanilla "class compliant" drivers.)
TB enjoys all the benefits of PCIe (because it is PCIe) - very efficient interrupt handlers, Direct Memory Access, and a very mature driver framework. So even though we'll never use 20 GBit/second of bandwidth - which would be over 9000 (if I did the math correctly) channels of 24 bit, 96KHz audio.
But that's not the point, is it?
No, the point is some folks - myself included - would dearly love to have an Apollo interface if only to gain access to the Unison Microphone technology. And today that means one of two Firewire cards that are approved, if you are running Windows. Could UA add microphone inputs and A/D converters to their PCIe cards? Probably, but how big would that market be? Oops... speculating...
Some folks complain about using Firewire over TB, but that's nothing new. I used to network my studio computers together using TCP/IP over Firewire. One has to separate the protocol layer(s) from the physical layer. I think the criticism about FW over TB is overstated.
As far as who is at fault, UA or MS, that's a business decision that is way above my pay grade. I can understand a small developer wanting to wait for official support. Developing your own has several risks, and if I were UA I might consider that path, but I'd have to think long and hard about it. That's not faulting Lynx for gambling, and frankly I hope it works out for them, I think it will.
But I've now wandered into the realm of speculation, so I'm stopping here.