I believe it is an elaborate ruse personally. The big six are posturing for their own interests and (I hope) they are not likely to actually follow through. They are bullying UEFA into some serious reforms that will benefit them as profit spinning mega brands, like American style sporting franchises.
At least I hope it's this. As stomach churning as these 6 self styled "footballing oligarchs" are with their ongoing manipulation of UEFA (e.g. the way Man City and Chelsea continue to dodge severe punishment for FFP and transfer wrangling is disgraceful), this periodic spasmodic bullying rage is far more preferable to them forming a breakaway league altogether.
I hope you're right. Football players do this sort of power play all the time, threatening to leave to force the club to offer a superior contract etc. Why wouldn't clubs do the same?