A wage cap really is something that needs to come in. As Peter said, it is hard to enforce, but I think we're within 5 years of the game becoming a farce with who can realistically win competitions.
In Spain, due to the way TV rights are distributed, a huge wedge of the money goes to Real Madrid and Barcelona. So there, the league will basically alternate between these two.
In this country, this is essentially between 4 teams, but I can see it alternating between Man City and Chelsea if the financial situation continues.
The big problem with enforcement is that it must be a worldwide cap, otherwise we'd have the best players deserting the country. It works supremely well in Rugby League with several teams who can win it, despite some questions over bending the rules initially - e.g. family members being paid separately.