Don't be surprised if the next few seasons see a substantially lower quality of football.
A lot of teams will start next season not properly rested from last season. They will then be expected to complete all the games they would under usual circumstances but in a shorter space of time.
In 2021 all the top players will end up playing in the Euros, the Copa America and the African Cup of nations.
It seems inevitable that the best players will be overplayed and develop injuries. Even if they don't, the ones who get furthest in international competition will have little vacation time.
Once that's done players will be looking forward to the 2022 World Cup, which will see more calendar changes to accommodate playing in winter.
After the 2022 Winter World Cup players will be expected to go back to their clubs and continue playing at a high level, domestically and in Europe.
Its mad. I fail to see how teams can maintain a high level in these circumstances.
IMO over the next few seasons the thing that is likeliest to affect performance are a) squad size and b) number of games. Big clubs who have big squads and sack off the domestic cup competitions are likeliest to get to May in good shape. However, even then, as these clubs have a lot of internationals they will still likely get injuries to their key players at the worst times for them.