It means 2018, which will come in March 2018 (or possibly early April).
That is a completely separate tax return, so you can finish up your Federal and Minnesota income tax returns now. When you receive the property tax statement in March, you can come back and finish up the property tax return (which is not due until August 15th).
Just a reminder: The property tax return (Form M1PR) must be MAILED. It can not be e-filed through TurboTax. Another option is to e-file it through the MN website here: https://www.mndor.state.mn.us/tp/propertytaxrefund/_/?Reset=1
