Would be a little strange for Cameron to up and quit if he thought they could just ignore this vote, right?
I also understood this to be non-binding, but Cameron resigning was very shocking.
I would have called for his resignation regardless of the way the vote went. There was no need for him to call for it originally (except for his own little bullshit power plays within his own party), and his strategy for backing the remain campaign was farcical to the point that a paranoid person might ask if he purposefully did his best to de-rail the remain campaign. This referendum risked gambling a reasonably healthy economy for a big fat unknown; a reasonable person might wonder who on earth would go for that, but apparently there are a lot of fucking gullible people out there and enough bullshit to go around.
A successful remain vote would have achieved nothing useful (unless it picked up say 80% of the votes: that would have told the euro sceptics to STFU and stop stirring shit up) aside from maintaining the status quo, and a successful brexit vote means all three main UK parties have either imploded or are about to. The only party with a significant number of seats will be the SNP, which will soon call for a second Scottish referendum, so they'll be pretty irrelevant as far as UK politics go.
I also predict that the next election will involve a coalition with UKIP (a far right party that dresses themselves up a little smarter than most, whose leader once basically advocated letting immigrants who have HIV to die in the street), who will pick up a fair number of seats in the next election because the closet racists will be emboldened by the outcome of this referendum.