Unfortunately no. Airfare pricing is a game that even those of us who have nothing to do but talk about aviation travel can't crack. I've seen flights sell with an 80% full cabin for next week for less than half of what a 25% full cabin on the same flight will sell for in 2 months. In fact, using my EWR-SFO trip in November as an example, there are over 8 flights available on the day I want to travel, and Biz seats range from $825 to over $2,000.

I will say this: A $500.00 upgrade from even PE to Biz is an out of this world bargain to me (Assuming the PE price isn't a ridiculous one). If you want to fly in Biz, I second the others and say to pay the difference and take it up later, as this opportunity won't last for long. There is a chance you will get stuck having to pay the $500.00, but if Biz is that important to you, I wouldn't wait much longer.

Another way of looking at it. Assuming the worst case and you know you won't get your $500.00 back, is the J seat worth another $500.00 to you? Will you be happier paying the $500.00, or will you be happier in PE paying what you already paid?