I think it will surpass the record.
I couldn't believe that UFC 196 did 1.5 million buys because the UFC mishandled it at every turn, starting with dragging out the official announcement, then didn't promote that fight nearly as much as they should have. Really, RDA pulling out of the fight is probably what got it all the publicity for that number.
Since they will promote the hell out of UFC 200, Lesnar and the quality of the card, I think it will do around two million.
It's odd because there is numerous fighters on that card that should be getting PPV money. That's a good thing, but surprising from Zuffa.