Here's hoping that those theoretical MQA end-points will have MHR-enabled SPDIF outputs for pre-SL DSPs.
That must be likely - it can't make sense to produce one machine for SL speakers and another for non-SL speakers, and we have been told "that no one will be left behind".
I would have thought that the logical MQA compatible replacement for the MS200/MS600 would be something pitched between the two pricewise which offered the following:
1 SL outputs with the ability to toggle between MHR on and off
2 SPDIF outputs with the ability to toggle between MHR on and off
3 analogue outputs based on a 24/192 DAC with some trickle down from the 818v3
4 DSD capable via conversion to PCM
5 a cheaper case than the MS600 more in the style of the MS200 (but larger)
6 headphone capability
Setup options within config
SE speakers (full DAC management via 2 way comms)
SL speakers (DAC management up to 24/96 via 2 way comms)
Non SL 24 bit speakers (generic Meridian DAC assumed as no 2 way comms)
Non Meridian DAC (decoded MQA with no DAC management)
The last option requires the Auralic Aries issue to be resolved but it would make the MS300 (if I could call it that) much more saleable outside the Meridian ecosphere.
[no inside knowledge]