There or USA Mega. The cash value of the jackpot went up by about $38 million, and about 32 cents of each dollar goes to the jackpot. That means they're expecting sales of about 38/.32, or 120 million tickets. Because a lot of combinations will be duplicated, selling 120 million tickets would mean using about 95 million combinations if all were picked randomly, and 95 million is 54% of the total number of combinations.
Of course not all combinations are chosen randomly. It's really just a SWAG, but I'm guessing that all those non-random tickets will probably reduce the number of combinations played by at least a couple of million. That would mean that with 120 million tickets sold there will be about a 52 or 53% chance of a winner(s) and a 47 or 48% chance of a rollover.