Trouble is, you can't have a wages cap in the English leagues when they are competing with other leagues for players. They can have one in Baseball/NFL/Basketball, because noone else plays those sports. Rugby League has a wages cap, but their only competition is Rugby Union (which now also has a wages cap, after things went a bit mental in the early years of professional Rugby Union), and possibly Australian Rugby League.
Premiership (and to an extent Championship) teams are competing with French, German, Italian, Spanish, Brazilian, Mexican etc. football clubs when they try to sign a player. If we had a wages cap in the UK without an equivalent one in all other Leagues we compete with, we'd see a lot of players moving abroad for big bucks, like Kevin Keegan did back in the late 70s to Hamburg. Since this would also make it near impossible for English teams to compete in European competitions, I just can't see the Premier League ever agreeing to a salary cap.
My hope is that in the next 10 years or so we see a European/World Superleague formed, with the top 4/5 Prem clubs leaving to play weekly games against each other and Real Madrid, AC Milan, Bayern Munich, Boca Juniors, Sao Paolo etc - effectively what the G14 wanted back in the early 90s that lead to the "Champions" League. This would leave a rump of 15 roughly equal teams to compete for a league title they might actually have a chance of winning.
My fear is that instead we'd end up with a slimmed down top flight of 14/16 teams, with relegation either eliminated altogether (like the NFL) or reduced to one/two teams per season, and the "missing" games replaced by the "extra" games played overseas - what is currently referred to as the 39th game - Man U v Everton played in Dubai, Man City v Newcastle played in Singapore. All the teams below the top flight would then be reduced to "feeder" clubs for the top flight, along the same lines as college American Football is to the NFL (imagine Saints as a Pompey feeder club - eurgh).
If the latter is what happens, I shall completely lose interest in football, and go to watch Sale Sharks at Edgeley Park instead, or take up darts/snooker.