I suppose if we are going to have this discussion, we should be clear on what Cameron is 'renegotiating' on. This is it, there is no more detail available to the public as far as I know:
In broad brush strokes he wants:
1. An opt-out on the core EU aim of "ever closer union" including boosting the sovereignty and powers of national parliaments, so groups of them can block proposed EU legislation [my take - if the purpose of the EU is 'ever closer union' and we don't like it, we should leave]
2. To safeguard the interests of the UK as a country and specifically of the City of London and other financial centres outside the eurozone [ this looks anti competitive to me, and against the interests of the Eurozone countries. The City should remain a major centre because it offers better stuff, whatever that is, and is more competitive. Of course if we leave the EU we won't be able to 'safegaurd our interersts' as easily. We reached a decision (in a rather muddled way) to stay out of the Euro, we need to live with the consequences of that, many of which seem positive.]
3. To curb internal EU immigration by cutting benefits [I think he'll get this, but it doesn't answer the central question which is much more important to the electorate, how do we reduce immigration?]
4. To make the EU more streamlined and competitive [difficult to argue against in principle, what does it mean?]
Whatever the results, I doubt it will satisfy the anti EU Tories. I rather resent that this whole thing is really about an internal Conservative Party schism. I really don't think the general public is too bothered by the EU, except for immigration. Here's an idea on that - the UK legislates on it's own to restrict immigration and see if the EU then throws us out.
My understanding is Cameron will be happy with some kind of promise about EU legislation/treaty change prior to a UK referendum. Tory sceptics already saying that 'you can't trust the EU to deliver on a promise' as if the EU as a concept makes decisions rather than the people who run the EU - the heads of it member states. So really they are saying 'you can't trust the German, French, Italian etc government leaders.'. Probably true, you also can't trust the British Government of course.
Not sure whether tactically he is in a stronger or weaker position because of the two much bigger short term (hopefully) issues facing the EU - Greece and the boat people crisis.