if every other league followed suit. The talk about a salary cap is heating up in the wake of the Portsmouth debacle that has been this season. That coupled with the financial crisis makes it a great idea for the EPL. It would make the league more competitive and break up the big four. It is why the NFL is such a great league and MLB is so stratified.
However, it cannot be compared to American sports. The NFL is the top football league, same for MLB in baseball and NBA in basketball. They can do whatever they want with salaries because the best players go there and they can still far out-pay the rest of the world. The EPL does not have this advantage. If they started a cap and cut salaries players would leave to Spain, Italy, France or Germany. Competition would drop, performance in UEFA would fall and so on.
In order for it to work, all UEFA leagues would have to agree on the same salary cap. With such varying economies and cultures, the likelihood of this being adopted has to be at near zero. So, while the debate in England is nice and makes sense in many ways; it should not be implemented.