I think the clubs have badly miscalculated public feeling and I think UEFA, FIFA and the respective leagues are potentially buoyed by that.
I also think it's arguable that the clubs have overplayed their hand, in terms of leverage. The idea that the PL collapses if these six clubs move on, I don't buy. The product will, obviously be diminished but it's still a saleable product without those teams precisely because it'll have what the ESL won't - competition and a strong league overall.
Some fans on here think the world starts and stops at Man United and Liverpool but forget, Chelsea and Man City are just Everton or Newcastle with billions of pounds. Arsenal and Spurs don't have any more history that loads of other clubs. The rich owners will still be sniffing around the PL and see value in investing and a new "Big 6" may emerge. Millions watch average PL games worldwide every week.
In Spain, Barca and Real have had fortunes in state aid. Are the Spanish Government going to sit by and let them walk away and destroy the League structure? I doubt it.
The legal side will, obviously be extremely complex but all of the PL clubs will, I suspect be contracted to one another to compete in the PL competition. Steve Parish was on MNF last night and made the point that if those six clubs think they can go off and set up their own league, and break with the current contractual agreement, then the other 14 clubs could arguably do likewise and exclude them. The European side of it is more complex again, but as you say, the relevant bodies may well be prepared to put a real marker down.
The threat to stop players playing internationally is significant. Even if they set up their own competitions - how long does that take? Is it ever even viable? Where do all the other players come from you need to support it over and above a 12 team league? Would countries have two national teams and where would the rest of those players play, because it wouldn't be in the FIFA sanctioned leagues. It's a logistical nightmare and a nonsense idea from people who have no idea about football. And the vast majority of the players in the ESL won't be that much better paid (given the projections of income) to make it worthwhile not playing for your national team, especially if you can play for another team in the PL and still get a big salary.