I assume you are in US right now and in F1 status. So you should have new I-20 with the completion date stated. You don't need visa to stay here as long as you have non-expired I-20 (you can check the completion date in I-20) if you are back in F1 status.

You need visa only to re-enter US. So if you are planning to go out of US then u need to apply for Visa to come back. So as long as you are staying here and have valid I-20, then you are fine.