March 30th 2020: Device OS v1.5.0
A new Default Release Device OS v1.5.0 is available now on https://build.particle.io for Photon/P1/Electron/Argon/Boron/Xenon/B SoM/B5 SoM.
1.5.0
DEPRECATION
- Spark Core End-Of-Life. 1.5.x+ releases no longer support Spark Core #2003
FEATURES
Some of the feature highlights of this release:
- Sleep 2.0
- Higher level power management API
- Configurable I2C buffers and over 255 byte transfer support
- Thread-safe cloud variables and function-based cloud variables
- Chrono literals
And many more enhancements and bugfixes! 
Be sure to read the full collection of release notes Particle Device OS Updates Thread.