The IAP plugin currently uses PBL 1.2.

This library is being deprecated and replaced by PBL 2.0.

We've been getting reports of developers getting the following warning when submitting their apps to the play store:

We’ve detected that your app is using an old version of the Google Play Developer API. From December 1 2019, versions 1 and 2 of this API will no longer be available. Update to version 3 before this date.

Edited(cyanglaz):
The design doc for this migration can be found here:
https://docs.google.com/document/d/1XM16UsLE_aPWoZnheE9waO06mhxLkkWjpPf9jtI1AdY/edit?usp=sharing