If the quest for higher SINAD (or other benchmark) stops, what will be the next development? Its either features or performance that will incentivise someone to buy a new DAC. Multichannel may well be a next big thing but I suspect its a way off being a driver for mass sales .We have done the "balanced" thing. Suspect MQA is stagnating
I suspect the D90 V2 will be a spec bump, but no idea what the D100 will have that the D90 doesnt.
Other than adding physical features, outputs, inproving build quality etc. I think DSP/software is the next logical step (like what RME has been putting in their products for years on the professional side of things). Yeah SINAD could still be improved but it's at a point now where we're way beyond diminishing returns at the most extreme use cases and with the newest chips being present in some of the cheapest products. The market is getting saturated with many well-performing products now so it would be nice to see more 'premium' products that have things like stepped attenuators without breaking the bank and without compromising on design or specs. That obviously also serves to help lower the price of existing ones. Adding system on a chip boards to products for more streaming options and better software to stream with, and adding ethernet/wifi to cheaper lines of products would increase their value as well.
I personally would also like to see more no-compromise DAC/amp/preamp combo units that spec as well as their counterparts, and even products with power amplification built in for better all in one solutions.