>Quick question for any experts reading this - do Oculus or VIVE use any sort of dead reckoning/movement prediction in their tracking? Also does anyone have any documentation on the APIs for this, or information on how the devices keep track of their latency and calibration information?

Absolutely. Vive uses a combination of IMU based dead reckoning combined with Lighthouse sensors to provide tracking. The dead reckoning is super important for maintaining tracking during sensor occlusion. The API it interfaces with is SteamVR, which is mostly open source, so you can even see how they’re doing it. The new generation Vive Pro will combine this along with stereo camera CV based inside out tracking for even better precision.