The 3.5mm jack will be very hard to give up. It always works, and (usually) there's no interference / hiss.
I find that digital devices are complicated enough that, unless I'm buying well-researched, high quality products, compatibility issues lead to glitches. I still encounter lots of glitches with Bluetooth, so I'm not ready to give up my trusty 3.5mm jack as a reliable fallback.
Furthermore, things like sampling rate and bit density will actually make supporting this somewhat complicated. If it's locked at 16 bit, 44.1khz; then the playback device needs to have an excellent noise shaper and sampling rate converter to play thing like "mastered for iTunes" that decode to floating point and assume a 24-bit DAC.
In contrast, if the format allows any bit per sample, and any sampling rate, then lots of compatibility issues will arise on cheaper devices.