https://developers.google.com/analytics/devguides/collection/upgrade/?hl=en_US

Universal Analytics is a set of technological innovations that improve the way data is collected and processed in Google Analytics.

The Universal Analytics Upgrade is a process you can use to upgrade all of your classic Google Analytics properties into Universal Analytics properties without losing any data or changing your account settings.

All Google Analytics properties will soon be required to use Universal Analytics. Any properties that don’t follow the upgrade process will be auto-transferred to Universal Analytics in the future.

The transition from classic Google Analytics to Universal Analytics is happening incrementally over several phases.
The current phase is Phase 3: Universal Analytics out of beta.
The next phase is Phase 4: Universal Analytics is the operating standard for Google Analytics.:

All properties have been upgraded into Universal Analytics.
The following features will be deprecated:
ga.js
urchin.js
WAP/server-side snippets
YT / MO
Custom variables
User defined variables
Data collected from the deprecated features will be processed for a minimum of 2 years.

Currently, JBT usage sends requests using ga.js format. We should investigate what's changed in Analytics.js. And get ready to migrate to that new format.