Flush Mount Ceiling/Wall Speakers
For the speakers, the ceiling mount speakers I have used have their own &quot;can&quot; and just need a hole in the drywall and wires. They are not designed to be trapped by the drywall, they are designed to be installed into it and can be removed from it when/if desired. You can get separate empty cans and speakers to put in them if desired - any AV supply place, ceiling mount speaker cans...
For the wires: Conduit. This stuff changes rapidly compared to other building systems. So, place conduit and easily update it when everything changes again (enough that you choose to upgrade).
Otherwise in 10 years you'll have the equivalent of a VGA cable and quadrophonic speaker cables stuck in the wall today - antiquated, though you might be able to kludge some use out of them.
While you are at dried in but no drywall, think about networking, and wiring wireless access points (which work best if they are wired and the things that connect to them can see them without going though walls.) Easy now, hard later. Nobody remembers to put networking in the ceilings, but that's where you want it to make your portable devices work well.