I'd like to see DSD go away forever, firstly. It is literally just as capable as HD PCM but forces the listener to invest in DSD converters to read the alternate language. Even Sony gave up on that grift. That there is already so much released in this alternate language is kind of sad. So SACD will always get last place from me.
Anything and everything comes off the mastering desk in 24 bit PCM. Let's keep it that way to start with. That obsoletes the old CD format. Download and then a bluray for a physical format makes the most sense now. Easiest to rip and burn. DVDA, the various encoding schemes used on DVDV, and SACD all require more tech skills to rip with no or least loss.
So... someone decides some content is fine to reduce to 16 bit just to entertain the old CD format. Why? I don't care if anyone can hear it and I don't care to have A/B shootouts every other day. Leave it 24 bit. Now release it. There! You did it!
CDs for the car seems like as fine an idea as it ever was. Everyone already burns disposable CDs for the car for that, right? You wouldn't actually throw a purchased CD in the car anyway, right? Just burn em from the download or bluray. Or make mp3s for the iThing.
Frankly, all these formats - even the lowly CD and some of the lossy encoded formats for surround (eg dts2496) - are excellent containers for music. The above is my academic answer. My first comment is we need more consistent mastering prowess to eliminate the trashy shrill volume war crap that sounds terrible in any format. That's the consistent problem that makes any talk between these formats a moot point. The old analog encoding schemes actually did real damage to the music with best efforts. None of the modern digital formats come close to this kind of destruction. Not even the worst ones. There may be examples of conversions on the fly in different media players that DO get down to that level but the discriminating consumer still has the option to extract the music properly now.
We don't need format discussions, we need more mastering critique with teeth!