I predict that:
(1) Leave wins narrowly,
(1a) Because the polls are showing what I think will be the ultimate narrow margin of victory, but the polls are missing some support for Leave because of the Bradley Effect and some support for Remain because of voter fraud and non-citizen voting, the two will cancel each other out
(2) David Cameron will refuse to implement the formal procedures to exit the EU, based on some pretense, either:
(2a) Openly citing the “whiteness” as the Leave electorate and the “rainbow/diverse” nature of the Remain electorate as an excuse, or citing the narrow margin of the Leave win, or citing the Jo Cox murder, or some combination thereof
(2b) He will, for public consumption, and while engaging in superficial but non-substantive measures, pretend to be exiting the EU, in private and behind the curtains, not doing so in substance.
All polls close at 4 PM Central Time, 10 PM local British summer time, and I expect as usual, the same few constituencies that historically hurry up and count after closing, like Sunderland and a few others, will follow suit here, even though the vote is country-wide, and not a per-constituency affair like parliamentary elections. However, it won’t be until late in the evening our time that constituencies start reporting en masse.