The rebate is directly from Bestop, and it will definitely end on the 31st. Vendors like 4wd also have their own promotions and deals, and of course they do that throughout the year.
And, in fairness, it should be mentioned that the Sailcloth is a replacement top - it's just the fabric and windows, not the hardware. Which works great and is an awesome deal when you already have the factory hardware. If you don't have hardware, then it's a bit more. Still a great deal! :-)