Salary caps are about how your society values parity in whichever sport it is applied to. Regardless of the salary cap argument, do expect this to affect soccer as well, though further into the future. Right now many of those salaries, bumps for league promotion, etc are based on similar revenue sharing based on TV deals. And as US soccer eyeballs have grown, US TV deals have just added dollars to the already existing and new TV deals in soccer. They are on the upswing at the moment (kinda), but as fans get fed up with these draconian viewership requirements they are going to have to fight for the same in-between viewers (i.e. ones that would watch, but don't have to at all costs) that US sports are vying for across new mediums.
I should clarify that it won't affect the top teams in these situations. Man U and Barca and what not will still be fine due to ancillary sales and their brand. Rather it will affect the vast majority of other teams. Some owners are willing to take a hit, but only so much and for so long (except the super rich ones for which their team is their play thing).
