Well, games are for enteretainment, first and foremost. They provide friendly competition (though you can't see that in a lot of online games, due to all the cussing and whining). Professioanl gaming would be an interesting concept, but I really don't know if that would happen.
Like stealth toilet said, developers and companies (mostly microsoft) are concerned about making the most money by making it the "in" thing to do. This idea is probaby the reason for the mass consumption of th enew 360. No offense, but I really think that there would only be a fraction of sales for people who actually want it, rather than just to have it so they can be cool.
Another point stealth toilet made was that there is a generational gap right now. Most of the older people hate video games, can't play, don't care or whatever, while the younger generations are pretty much being brought up on them. So, give it time adn I think there may be some leagues out there and it may become a professional thing.
At first, I agree with stealth toilet, and there would be a lot of commercialism. This could last for years, and could actually break the whole thing. But if the pro leagues and the system made it in tact, commercialsim may move on to something new.
If we look at other pro events, we can see. For al ong time, Billiards was a huge thing. People made big bucks by doing it, but today, its just an hour event on ESPN2 to take up some time. True, they still can make a lot of money doing it, but all the commercialism has fallen away from it.
I would like to make comments about the X-Games, but I'm afraid of getting things mixed up. My feelings is that when it first entered, there wasn't a whole lot of commercialism with it. But when it got big, you knew it. There were new brand names every day, there were tons of movies about it and stuff, lots of video games were made, and so on. But that seemed to be a spike the receded quickly. Theres still a lot of advertising to go with it, and its still one of those "hip" things to do, but its fallen away a bit.
So, if video games became a pro event, I could see the same thing happening. However, I have no idea how long it owuld take before advertisers fell away from it and it returned to what it is now, a source of entertainment (and controversy). Obviously, video games are here to stay. Whether or not the become a pro event, there will always be controversy about them. Maybe if they did go pro, it would be fuel for controversy, but I don't think anything too serious would happen.
But I can't predict the future.