Since it is generally accepted that what sounds good is entirely subjective it is impossible to say for definite that any guitar will "improve". The question is will the sound change? On a solid spruce top, Yes it will. On a cedar top, unlikely. On a Plywood or other top, unlikely. On an electric guitar the sound is largely also a product of the pickups so you are then introducing a whole new set of variables such as magnetic field decay, any change in the copper in the windings and the changes to any potting of the coils that happens over time.
Best advice is just enjoy your guitar unless you are a maker in which case you should shoot for a decent sound to start using what experience you have. The sound of a completed guitar will not suddenly drop off unless there is some obvious reason. Do not believe any one who suggests that they can predict how the sound may "open up[" or "change". They can't any more than they can predict next weeks lotto numbers...