How High Would Mega Millions Have Become If No One Hit The $640 Million Jackpot?

At least one winning ticket was sold, but hypothetically speaking, how high would the next jackpot have been? Could it have reached a billion if the winning ticket wasn't sold?

I always buy a ticket, even when it's at it's lowest $12 million dollar jackpot. What I do is buy one ticket for 15 draws, which is the most draws you can buy at a time in Missouri. I only buy one though. It just so happened that I needed to buy my next ticket this week, and the guy in front of me in line purchased $500.00 in tickets.

This got me thinking, could there reach a time when it didn't grow much because everyone was tapped out trying to win the last jackpot? I mean that stupid guy that laid down $500.00, would he really be able to lay down another $500.00 three days later? I'm wondering if people would have been able to keep it growing so dramatically if no one hit the $640 million dollar jackpot.