if (a big "if/when") this breakaway league does happen, things would likely continue as is initially imo re the cl qualification spots and pl. if the "founders" are no longer in the pl, whoever finishes top 4 of the remaining teams will qualify for cl. but it would likely feel like a europa league campaign, and within a year or so, the finances generated by the competition will reflect this.
i reckon, the "founders" will still remain in the pl though. they will essentially use it as a reserve league, and put their youngsters in there. it makes sense for all that these teams remain in the pl imo.
all the money will end up in the superleague and the pl will become a shadow of what it is now. the gap in quality between the super league and the pl will be huge, and the salaries of the players will reflect this.
i think the super league scenario could actually be quite good for fans. fans of teams like man utd will surely want their team in the super league, so no issues there. but for the rest of us, this should lead o a dramatic fall in ticket/tv prices to follow our teams.