A promise as large as a referendum doesn't get forgotten. Not having one would have basically assured no Conservative government in 2020, so from Dave's perspective it had to be done.
It's now all about how Brussels want to take this: Keep the UK as a key client for a lot of German and French exports at the cost of looking lenient and risk countries like Greece and Italy with their own independence movements gathering traction or try to make an example of the UK and risk losing a great deal of trade. Obviously it's going to fall somewhere in the middle, but the initial murmurs from Germany are that they want to approach this cautiously. My feeling is that they're going to have some extremely drawn-out conversations over the next 12 months and there's going to be the usual trickle of information feeding into the public.
Wild speculation: I think they're going to remove a lot of the social benefits and keep the economical ones. i.e. removing the right to free movement without a visa, but leaving current trade deals largely intact. The EU doesn't want a recession, but they still have to look like they're sticking it to the UK a bit - largely social benefit removal would be a good way to do this. Making a big fuss over withdrawing the money they send us for infrastructure etc. because it'll make headline but ultimately isn't a huge deal like some of the more complex trade is.
Still, really wanted to see a properly united Europe with the fat trimmed off (low economic performers with semi-corrupt governments like Greece) and a centralised government that doesn't just dip its hand in when it wants to like Brussels does/did, but is instead a fairly elected and properly weighted parliament based on concentration of population (i.e. the UK - for example - would get more representation as it has a far denser population than say Czech Republic. State system like the US in that state-level laws can still be made. My opinion is still that we could have worked towards this quicker from the inside, but yeh.
I just feel like the vote last week has meant I will never see this in my lifetime now, and that's pretty saddening. It's the natural course of things for countries to merge and for larger territories to be governed by a single system (it's just always going to be more efficient), and I think this is going to be the wake-up call for the EU to start reforming the way it governs. It's just a shame that we had to be the ones on the outside rather than any other country.