Hopefully they’ll keep the fees low (or even lower them) for devs with free apps. I don’t think they’ll front load unless they can estimate the revenue of an app. They’ll make it a monthly payment based on app revenue or some other indicatorI think it’s more likely Apple will front load the fees if the commission % goes down. I’m sure they’ve done all sorts of analysis to work out how they would need to tinker with the figures to make up for lost revenue.
Sadly, front loading the developer fees will make it harder for small time developers to ever get started. It would effectively be the de-democratisation of the App Store.