They'll just make less money. Visa doesnt lend money, they charge transaction fees. the transactions are said to be going higher in numbers and lower in amounts. So they could make more money or less. I would reccomend everyone buy it and get put/leaps on it for market insurance. of course I dont know how long before the puts come out, so it may be prudent to have a tight stop loss. Companies like this usually go public for one reason, to sell it. So It is a pretty good bet that the bag they are holding is their own company.
The banks that own Visa are cashing out. The proceeds are going to pay of debt, legal settlements and to existing shareholders. It may be a good short candidate.
Not to mentuon that even if they only make profits through transaction fees...once the credit crunch really kicks everyone ass in the credit card industry (ie everyone finally defaults or has their cards closed)..then Visa's profits in theory would drop like a rock. I'm not a stock whiz as you can probably tell..this is just my general opinion based on my limited knowledge.
If this gets as overhyped as say a BX, it will be a huge dissapointment long term. Everyone one will expect MA type results and they will have their thumbs up their ass.
Of course the Visa IPO is overhyped. IPO's are designed to make as much money for the company as possible and are therefore sold to the public at the highest price possible.