Something I'd really like to see with the M2 that I haven't seen mentioned yet is:
-A move to the ARMv9-A instruction set
Back with the A7, Apple basically pioneered AArch64 (being the first implementation by almost a year.) While Apple Silicon is certainly pushing ARM in completely new ways on the desktop (their interconnect technology is insane for example) it'd be nice to see them stay ahead of the curve as far as the base ARM feature-set is concerned.
(Not a software dev but the new Scalable Vector Extension 2 (SVE2) and Scalable Matrix Extension (SME) both sound nice, as do some of the other features.)
One of the difficulties I feel we're already seeing with Apple Silicon is that Apple has a bunch of proprietary tech that, while really cool, is going to take a lot of work for devs to get the most out of. Putting some energy into having the latest ARM features would hopefully take some of the pressure off both by ensuring that we get to take advantage of the latest optimizations devs are making for use across the entire ARM ecosystem, while also putting Apple in a position where it can leverage its position to push for faster adoption of those features.
Obviously for this to happen I'd imagine the A16 would have to be based on v9, and the M2 based on that. I don't know that the likelihood is super high but hey, I can dream right
Also just to reiterate what's already been said by others the M2 really needs to have support for at least 2 (external) displays (3 including the internal) on the base configurations (or, even better decouple # of displays supported from the SOC config.)