Yes; in fact they have videos showing the whole stack re-entering and doing a propulsive landing (one at a time, of course.)
The second stage will need a re-entry heat shield, but otherwise can land like the first. Tricky part is getting enough margin in the second stage for the landing fuel and legs and heat shield. Usually the top stage is the one you optimize most heavily. So plausible, but tricky.
Good news is that the second stage is much cheaper than the first, at least on the F9. Eight fewer engines, for one.
(I didn't know that)