Yes, treasure chests respawn. There's no set timer. A chest sits on a respawn point, and another chest will pop up there eventually.

From observation, I believe that the system doles out chests in a zone in a way that controls both how many are spawned and how many are on the map at any given time. So, hypothetically, if a player opens a Cyrodiil chest the system will see one less on the map. If it hasn't given out too many a timer will run, and then when the time is up a chest will spawn via RNG at any empty chest node...not at the node the chest was opened at.