When Samsung released the Galaxy S6 it traded expandability for build quality. No micro SD card slot, no replaceable battery, no removable rear cover.
It turns out that none of those things matter.
Samsung provided a base of 32GB storage, which answered most users concerns about the memory expansion. It enabled two fast charging methods and wireless charging so battery life was not a problem for most users. And it offered a variety of S-View covers that didn't need to replace the phone's back cover to work.
So when Samsung releases the Galaxy S7 early next year I'll be quite happy to see these absences continue.
What I would like to see return is MHL - the capability to output video over the micro-USB port.
This capability isn't something that I can say hand on heart that I've used regularly, however it can prove to be a lifesaver, for delivering the unexpected presentation, or even creating a quick RDP terminal with a Bluetooth keyboard and mouse.
Samsung demonstrated the capability of this kind of solution when it released its desktop dock for the Galaxy Note 2 - a dock which clearly influenced Microsoft to deliver Continuum, given that the Lumia dock delivers almost identical functionality.
So I'd be very grateful Samsung, if you could drop a shiny new MHL 3.0 connection into the Galaxy S7, which would give me a very good reason for upgrading.