I usually note from time to time the culture required for my current bonus and the next.
And so far culture required between 120% bonus and 140% bonus is already almost the same value (always the same more or less 100 culture)
Exemple with my city 2 days ago :
to reach 120% I needed 1700 available culture
to reach 140% I needed 3500 available culture
to reach 170% I needed 7000 available culture
never been able to reach 200% bonus since a long time
So with the new system it should be (if I understood correctly) :
to reach 125% I needed 1700 available culture (same culture required for 5% more coins/supplies)
to reach 150% I needed 3400 available culture (10% more coins/supplies for less 100 culture)
to reach 160% I needed 5100 available culture (a lot less culture needed for this bonus, but less 10% coins/supplies)
to reach 170% I needed 6800 available culture (less 200 culture for this bonus compared to before)
no more 200% bonus (less 30% coins/supplies for people who are currently at 200%)
So I'm not sure this will solve anything...
In some case it could give a little more coins/supplies, but I'm not sure it'll be worth to build more cultural buildings to get these bonus.
I'll probably just stay at 100%. We'll see next week.
But thank you to developpers who try to improve this