Project Treble is Google's plan to keep the drivers working - I don't know how well that's going seeing that OEMs were given the option to not support it at the time it was launched.
For a good example of this, see the conclusion of this recent Project Zero writeup of an Android bug (related to old kernel versions in Android, in fact): https://googleprojectzero.blogspot.com/2019/11/bad-binder-an... First, Google Project Zero determined on their own that they would approach Google Android with a 7-day disclosure timeline because of active exploitation - usually a disclosure timeline is a way to force the hand of a software vendor you don't control. Second, their suggestion for fixing it is for Android to change how they approach kernel updates.
For another good example, see the time that Google Ads penalized Google Chrome for buying paid links. https://searchengineland.com/google-chromes-paid-link-penalt...
I thought you were going to say that they're working to open source the drivers.
For what it's worth, Google (or at least parts of Google) agrees that the closed-source drivers are a problem for extended security lifecycle, and they're working with the Linux community to a) extend the kernel LTS cycle to 6 years b) make something that looks awfully like a stable API/ABI for drivers so that Android can upgrade you to a later point release of that LTS without requiring additional work from the hardware manufacturer. https://arstechnica.com/gadgets/2019/11/google-outlines-plan...