The question is academic.
There will be no need for further EU treaties. The Lisbon Treaty (and, yes, I have read it) gives the EU all the power it needs to control virtually every aspect of the member nation’s economy and there is already talk (without mention of a new Treaty) that the EU will in future need to “sign off” the UK’s budget proposals, with the power to veto anything they do not like.
The only fly in the ointment is that the UK is not a member of the Euro bloc and it makes life a little inconvenient for France and Germany to make decisions whilst this persists, particularly if they want more cash. (The UK’s contributions to the EU have recently been raised from £6bn to £9bn under another pretext). Nonetheless, Cameron was on absolutely safe ground when he suggested that any future treaties would be subject to a referendum. He knows, as do all politicians, that there will be none. There is no need.
Accordingly, the only issue surrounding Europe that may tear the Tories asunder is if enough cross-party support can be mustered to propose that the UK leaves the EU. There is far less chance of this than of Portsmouth avoiding relegation this season.