I was waiting for this one to come up 
The major delay (across the board) was MQA and that single feature on the Rossini tied up our development partners for many months last year. The complexity there surrounds the way in which our implementation handles clocking which is somewhat different from other integrated streaming platforms. The Rossini was implemented first and released in December. Vivaldi One is the next platform in line and that’s in verification now. Network Bridge is next.
In addition to MQA this release is slated to include USB audio output as well as the ability for the bridge to issue control instructions to a dCS DAC (i.e. volume control, filter selection, etc). There are also a number of bugfixes and general improvements to the code. If we hit a major snag that’s going to prolong things too much we may make some adjustments to the planned feature list.
I’ve had a working development version of the MQA firmware for a couple of months and it’s solid. We started testing USB audio builds a couple of weeks ago and although there are some issues to iron out it’s looking good. I can’t promise a release date (learning from the Roon guys on that one), but I can say that once Vivaldi One is done all resources will focus on NBR.
We don’t plan sound quality improvements as we try really hard to get that part right from the start 
AirPlay 2 isn’t planned at this time, but may happen in the future. Apple just pulled AirPlay 2 from iOS last week so that’s a pretty strong indication that the code isn’t fully baked yet.