I'd tend to disagree. Many gamers, like myself, buy everything nfl. Madden sales would go down, but not anywhere near half. I don't think 2k managed more than 35% of the market in 2005.
The money being poured into the exclusive license isn't chump change either. If they went the old route, the savings would probably make up for the loss in sales and also give the developers a bigger budget to work with for improving their game.