What to do with rental if CO is delayed?

[Frederick Wright]

I had a house fire last July and have been renting a house while my original house is being rebuilt.   The construction guys tell me they should be done and i should get the certificate of occupancy on 5/30/17 so i'm planning on moving back on 6/3/17.  However, i know how construction guys are and i'm wondering what happens if it gets delayed.  I have to give my landlord 30 days notice and i really want to do that as he's been good to me.  However, what if i tell him i'm moving on 6/3/17, the CO gets delayed and the landlord already has someone moving in on that day?  Am i out on the street?  What are my options at that point?