If you already have good eyesight but you get lasik eye surgery, might your sight become even better?

No: Lasik corrects a "error" in your visual system such as near or farsightedness---if you have none of these, then there really is no reason for surgeon since there is nothing to improve.

Not usually: Lasik is not done to give you super-normal vision; it is done to correct an error in your prescription. If you are fortunate enough to have naturally clear eyesight, enjoy it! and leave well enough alone.