The companies and devs will utilize the option for sideloading, it won’t be up to us. They’ll create their own app stores and have sideloading for many apps/games to get around paying Apple. Also as another user mentioned, being able to keep tabs on all our subscriptions through our Apple ID is amazing. When they allow third party payments that will be over, and companies won’t be passing the 30% savings on to the consumer, I can tell you that.
Also, big picture: currently Apple makes money mostly by selling hardware, then ~25% from services including the App Store. Google, Meta etc make money through user data and ads. Currently Apple has little need for ads or to sell user data, however, take away their App Store revenue, and disincentivize hardware sales (through things like making iMessage for Android), and Apple will need to look for other avenues to replace that revenue.
I can tell you we aren’t going to like it when they do. We already complain about the little bit of advertising we get now…