Getting Large Federal & State Refunds but still waiting on K-1

I am getting a large refund for Federal & State Taxes. However I am still waiting on a K-1 which I have been told I will not receive until the summer. This K-1 will have minimal income so I will still be receiving refunds. Do I file what I have and then do an an amendment or do I wait until I have the K-1?  Do I need to file an extension if I am receiving a refund or do I just wait to file? I want to limit audit risk. Thanks!