Your best option is to file an extension, if you don't think you will have the K-1 prior to April 18th this year. If you file without it, you will have to amend your tax return later when you receive your K-1 Form. The extension allows you an additional 6 months to file your tax return. You will likely receive your K-1 before then.
How do I file an extension (Form 4868) in TurboTax online?
https://ttlc.intuit.com/replies/3301811
Remember that an extension
is simply an extension of time to file your return. It is not an extension of time
to pay your tax due. If you will owe this year you should
make a payment with your extension to avoid penalties and interest.
