I have a Schedule K-1 indicating that I will be receiving a Schedule K-3, which it says will not be available until June. How do I handle this since it's past 4/15?

It depends. If you believe Schedule K-3 will report sufficient income to affect your taxable income for the year, you may choose to request an extension of time to file. But if you believe the information from Schedule 3 won't apply to you or won't significantly change your taxable income, you may choose to file your return now and amend your return if necessary when the forms arrive.

In most cases, the foreign income reported on Schedule K-3 is either already reported on Schedule K-1 or only applies to partners with other foreign income and/or assets.

If you chose to file now, uncheck Box 14/16 from Schedule K-1 to clear any federal review issues in TurboTax.