The Linux developer community promised almost 20 years ago [1] that no release of the stable kernel will ever break something that worked in a stable kernel before. AFAICT, this promise holds. If you upstream your driver, the community will take care (cf. AMD), if you don't your users experience occasional pain (cf. NVidia).

[1] http://kroah.com/log/blog/2018/02/05/linux-kernel-release-mo...