I'd say it is past negotiations. The referendum probably puts them actually now in the weaker position. If people opt for the EU, Brussels could easily ignore any claims for further privileges, after all the EU has been officially backed by the British people.

And if people opt for leaving, well, then the decision is clear anyhow.

As for the vote next week, I have no idea what to expect. At the last debate Cameron-vs-Farage, I did have the feeling that Cameron was slightly nervous - but that was just a subjective impression.