Not to sure about that, Jean - Claude Juncker came out and said this yesterday:
http://www.telegraph.co.uk/news/2016/06/22/juncker-tells-britain-you-wont-get-a-better-deal/
David Cameron’s pledge to reform freedom of movement was undermined by Jean-Claude Juncker yesterday, who said there could be no changes to the renegotiation deal he was given in February.
The president of the European Commission said Mr Cameron had been given the “maximum he could receive” and said there could be “no kind of renegotiation”.
The remarks were intended to discourage British voters from supporting the Leave campaign in the belief they could return to Brussels and demand a more generous deal.
“Out is out,” Mr Juncker said.
Mr Juncker said: "The British policy makers and the British people have to know that there will be no kind of renegotiations.
“We concluded a deal with the Prime Minister. He got the maximum he could receive and we gave the maximum we could give, so there will be no kind of renegotiation, on the agreement we found I think in February nor as far as any treaty negotiation [is concerned]. Out is out."