Yeah good that you came up with this again, there hasn't been a statement on free apps with ads from any of the team so far.
I am not sure how would the profits would be distributed if devs got money via google ads for example. That would be confusing as hell to distribute and explaining in taxes why are using your income from google to buying cryptocurrencies and sending them to anonymous people.
What benefits can a developer obtain from the App store if his or her app is published for free and vice versa?
Yes, it woul be nice. they must have a huge users base at first.