An update on the Android problem

Galaxy Nexus was the first of the Nexus / Google-partnered devices to not receive a kernel upgrade, I believe (the Motorola Xoom tablet was probably the last to do so). Galaxy Nexus was largely a victim of the SoC vendor trying to do the right thing: TI engaged the kernel community to upstream much of the SoC support code, plus the remoteproc framework and other stuff written as part of that project. But the resulting large differences in code bases between the tested shipping code and the upstream code, and the likelihood of requiring a substantial effort to get the upstream version to product quality, caused a kernel upgrade to be deemed not worth the effort. (I believe the XDA folks wrestled with this for their firmware and ended up reverting a bunch of stuff done upstream.)

This situation reportedly continues to be the case for most if not all major SoC vendors: the internal trees used to produce products differ heavily from the code that undergoes community back-and-forth and gains acceptance upstream. The two codebases just can't be allowed to diverge very far, and that requires an ongoing level of investment that can be difficult to justify.