Tenant informs me that they MAY move out in a month

[Dave S.]

Looking for some advice as my wife and I recently took over as property managers to our rental portfolio. One of our tenants reached out to let us know ..."So it is 90% that we will be moving April 1st. We will know for sure tomorrow". This was received on March 4th...already into the 30 day required notice. As of the 6th, we still dont have a definitive answer! Im looking at it from a business, and time is money. Every day counts. Im holding off marketing the property. So i have a couple questions: 

1) Is the text I received notice enough about moving out? Or do they have to sign something? (which would definitely clear up future move outs!)

2) Suggestions on next steps...its more difficult as we befriended the tenants as well. Also as some history...the tenants have been great and lived there for 3 years.

Looking forward to hearing what others think

Thanks