Google has sent notifications out to G Suite customers that in starting next week, a warning will show up in Google Hangouts that SMS will no longer be supported. That support will end on May 22nd. The notification and change is part of the overall strategy of Google to move their G Suite customers to the new Google Hangouts Meet and Hangouts Chat while leveraging Android Messages for SMS on Android devices. For consumers, the focus is on Google Allo and Duo to meet these communications needs.
For those readers who are on Project Fi (I am one of them) or using Google Voice, this change does not impact you. This change only impacts G Suite customers who are using carrier numbers to send and receive SMS messages. This fits along with what Google told me earlier this month at the Google Next Cloud event in San Francisco.