Significant changes are taking place in the Pixhawk / PX4 / Ardupilot community with regard to on-board vehicle communication between the flight controller , electronic speed controllers, GPS units, and other devices.
Majority of systems in use today are based on legacy RC PWM (for motor outputs) and i2C (for GPS connectivity) which are rapidly becoming outdated and unable to cope with the reliability and performance requirements in the future. 72% of respondents polled by dronecode reported using RC PWM for their propulsion system. GPS connectivity is also largely based on i2C which is prone to noise and interference.
The future of on-board UAVCAN communication is gravitating towards UAVCAN which was developed by Pavel Kirienko. Below is a link to a presentation given by Pavel Kirienko (Zubax) and Scott Dixon (Amazon Prime Air) at the PX4 dev summit in Zurich on 20th June 2019.
On PX4 , UAVCAN is migrating from UAVCAN v0 to UAVCAN v1.
Video and slide links given.