Google recent sent out an e-mail to its Mobile Services partners indicating Hangouts will no longer be required to be bundled with hardware. Rather, video calling app Duo will take its place.
"Duo will replace Hangouts within the suite of core GMS apps, and Hangouts will become GMS Optional for telephony products," it reads. "This change will take effect on December 1, 2016."
What's also interesting is Google's text messaging app Allo isn't getting the nod alongside Duo; for whatever reason, the company is content to not push the text side of their new communication apps in this regard, at least for the time being.
In any case, Google will continue to support Hangouts; it simply won't be mandatory anymore on partner hardware.