The devil, as always, is in the details.
At the end of the day, any commitment is only as good as the cost of the penalty for breaking it and the belief that said penalty will actually apply. If the clubs believe that they will make enough money to justify paying the penalty, or if they believe that the penalty will not in actuality apply, they will likely do as they please.
Note that by "penalty" I don't exclusively mean whatever they commit to the league, as fan reaction and the implications for ticket sales, merchandise sales and lost viewing due to bad press are part of the penalty. So is any loss of personal prestige and social standing the owners might suffer.
It has come up time and again in these discussions that EU competition law is germane to these discussions. There is belief among some posters that those laws prohibit the domestic leagues, UEFA and FIFA from passing regulations whose purpose is to ensure that they are the only game in town.
That's likely to create a persistent credibility problem. There's the cultural heritage argument for why the clubs should effectively be compelled to be part of the existing system and pyramid. Against that is the financial argument of Perez and others that revenue is being foregone as things stand, that UEFA and the domestic leagues are not incentivized to realize that revenue, and that the cultural heritage argument is meaningless if the system collapses into chaos due to the financial pressures of the last year.
Like most of you, I tend to find the argument of Perez and his ilk disingenuous at best. It's not clear that the courts will agree, or that they will agree tomorrow even if they do agree today. One could argue that the sanest course for the big clubs is actually to drive the clubs to the brink of financial disaster, blame the competitive pressures of the present system, and ask the courts for relief in the form of the breakaway league and its guaranteed revenues...if that is not in actual fact precisely what they tried to do already.
So in a sense, I'm not really sure what the leagues can do, other than work to rebuild trust between them and the recalcitrant clubs while working to aggravate their distrust of Perez and the co-conspirators. Punishment for its own sake probably doesn't further that. Finding ways to grow the pie, enhance the competitiveness of the league and enhance the competitiveness of the English clubs in UEFA's competitions does.
From the perspective of the Prem, the objective should be to be so dominant in Europe, and yet so competitive within their own league, that Europe is a sideshow and the league games are where it's at. The trouble is figuring out how to get there when other major clubs have been permitted to vacuum up most of the available revenue within their uncompetitive, or barely competitive leagues.