Just in case anybody was still confused about this, those saying this will not be permitted by Apple are simply wrong.
It has always been permissible to take direct payments, through Paypal or otherwise, for services used outside of your app or for physical goods and in fact the use if IAP is expressly forbidden for this.
Just some examples of apps I have used that do this: Starbucks (card topups, direct card payment), Dominos Pizza (Paypal using embedded web view), Ocado grocery deliveries (direct card payment). Many other valid examples have been pointed out.
Conversely, if you are offering content or services to be used inside of your app, even if they can be used from other platforms (eg Netflix subscription or ebooks) you MUST use IAP.
All valid uses if this new Paypal SDK will accepted by Apple without issue. Developers using it to circumvent IAP (including "donation ware" models) will be rejected.
There is no conflict of interest because the things you must use IAP for and the things you must use third party payment mechanisms for are mutually exclusive.
Clear enough?