That assumes that the EU want to negotiate, or is even capable of negotiation. From the sounds of what happened to the Greeks when trying to talk about their financial troubles with the EU, what I am expecting is stonewalling and misinformation from the EU publicly blaming us for stalling talks whatever the UK does. When 2 years is up, we are out on our backsides.
What I can't work out is whether that is an argument that we should be staying in (because we are better off financially there) or out (because friends don't treat you like that).