No, I don't think it'll be prevented, but I wasn't using an exterior DAC in my scenario. I've got one or two of those (e.g. Line6 something a rather) but what I mean is using the iPhone's internal processing. Use hardware to trigger (via Lightning port) and listen with headphones (via headphone port). That scenario, which is one I use frequently, doesn't work in the new platform shown.
All the other DAC-type stuff should still work provided the iOS / Apple platform will support them (don't see why not). I've just been reluctant to purchase iDevice specific audio cards, so to speak, preferring the USB standard because I use a PC primarily.
This is also what I always do with my external DAC. I don't see how currently this will be prevented, if that's what you're suggesting.