I am 100% against any kind of tournament which doesn't reward merit, but the idea the club can just ignore it, or that the domestic 'top' clubs can just ignore City, is ridiculous. City are a big business & will have to be frontrunners either for or against. If they can't fight it, they will have to join it.
Where the power lies, is with all the other clubs who aren't invited. They get together & tell the others they are completely on their own, refuse to play them, kick them out of the various leagues, & cups, then the majority of fans in every country will have no interest in watching the euro 'superleague' & most fans of those clubs in it will be totally pissed off & want to play in the domestic leagues instead. Also the current tv deal will have a block on stuff like this happening anytime soon.
For that reason, I doubt this is about a 'superleague' as such. If one does occur, it will probably replace the Champions League, alongside the Prem & still involve qualification, but the 'old guard' will want an 'istree' clause inserted to try & give them an advantage, perhaps a playoff, for qualification.
This could be to discuss another tournament altogether, or to discuss the ramifications of the collapse of FIFA/UEFA or the schedule changes caused by the World Cup etc etc.
If all the non invited clubs in europe stand together, then they can destroy any closed shop 'superleague' imo.