Motorola started pushing Android 7.0 Nougat to the Moto G4 and G4 Plus in some markets, but not everyone has it yet. OTA updates are nice, but developers also want to have access to the open source code for system updates. At least that's available to everyone now in the form of a kernel source download.
The code is available on Motorola's GitHub page. The archives contain code for both phones, which are almost identical save for the camera and fingerprint sensor. If you're not trying to troubleshoot apps or develop ROMs, this code won't be of much use to you. No one is going to stop you if you want to download it anyway, though.
The release of Nougat kernel source hopefully means the wait for a full rollout of Android 7.0 is almost over. Keep an eye on your status bar for the OTA.
- Motorola GitHub