1. ensure you have continuous integration against both stable and latest versions of everything, with the stable set of all transitive dependencies defined on a per-project basis, and what gets used for releases.

2. people are expected to fix the latest build whenever they have spare cycles. The incentive is that it is part of the pipeline for code reviews and can only be bypassed by the project owner. This means you'll need to support both stable and latest concurrently (bumping stable is also an option to simplify the requirement).

3. if you added conditional support for old stable/new latest and latest was eventually made stable, you can refactor that code.