If a timing chain on a 2003 Camry comes off or breaks will it do engine damage on a 4-cylinder?

NO, the 2003 Camry 4 cylinder in NOT and interference engine. If the chain breaks you will just be stranded. A chain breaking is a very rare occurrence. You will hear noise and usually the engine will perform poorly long before the chain breaks. But as with any engine, it is possible for it to just break suddenly.