Yes, you shouldn't file a tax return that you know may likely contain incorrect or incomplete information. (Also, amending a return can be cumbersome and takes a while to process, so its best to avoid them whenever possible.)
For now, you can file an extension and be sure to include payment for any taxes due as an extension only gives you an extension of time to file - not to actually pay taxes due. If you have the rest of your return completed already, the estimated K-1 should be good enough to give you a confident estimate of taxes due, if any, so you can include the payment with your extension and then reconcile when you actually file your return.