Yes, exactly: USB Audio Class 2 with 16x16 I/O.
At the moment I/Os are on I2S. Thus, you can connect any PCB supporting I2S for interfacing (Analog, AES3/SPDIF, ADAT...). But, I want to make a change to TDM in order to save some data lines: 10 vs 4 lines for each 8 channel i/o port.
Mainly I have to do that because I don't have enough pins on my silicon to run more then 16i/o in i2s mode and I still want more i/o.
Linux: Yes. I want to support it. That's one reason why I'm doing this. I do run Linux in parallel with my MacOSX. I learned if you want to do multichannel audio on Linux your choices are very limited especially if you want to go via USB or FireWire.
What I don't know yet: Does Linux ALSA support implicit feedback for UAC2? For now I implemented implicit feedback because Apple recommends. Else I have to implement explicit feedback, too.
X2 sample rates will follow later but for now I'll stick with 48kHz until I have a fully working prototype with everything in a box.
But I'm planning to make the project open hardware. For the software I have to check first some legal stuff. I'm using source code for the USB-Chip which is not open source. It was delivered with the development environment and it is only allowed to give away the binary but not the source code. But that is still a long way to go and will not happen next week already that you see the project on GitHub.