As the buyer, you have certain rights per the contract. Did you ask for occupancy at close of escrow? If so, do not close escrow until you know sellers will be out. Make sure everything is in writing. Talk to your agent and try to make it a win-win situation for everyone involved!
There are steps in dealing with people who don't deal straight.
Consult an Attorney.
Some attorneys joke when they say it but these are the steps
violence. I hope you have a sense of humor. You didn't take the last step seriously did you? I hope not. It was meant as a joke.
This is a diffucult situation. Remind the sellers that they signed a legally binding contract and if the new owners cannot move in at the time specified on the contract they can be sued for breech of contract. If nothing else works hire someone to help move their stuff to their new place. Moving out of a house you never wanted to leave is never easy. What ever you do handle it with emapathy and understanding. Good luck to you.