RCS is a big upgrade over the text messaging that many of us have become accustomed to. After ending its life entirely, the company will focus its energy on building Messages, the RCS-capable app that adds modern functionality to SMS on Android - kinda like Apple's iMessage. In fact, 9to5Google claims that Google may have meant to announce the end of Allo sooner, but pushed it back when news leaked about its plans for Hangouts. Messages is getting or has gotten most of Allo's best features and will continue to see major development. With less than 50 million active users, it is safe to say that Allo didn't quite make the mark Google hoped it would. Furthermore, Google Duo is another high quality messaging app from Google which is one of the highest rated mobile application across iOS and Android as well. It hasn't received a major update in nearly one year and most of the Allo team has been moved to Android Messages.
As Google has done with previous platforms and services, it starts them up to learn the ins and outs until eventually Google applies what it learned from the failed product into a new one.
Google Duo, the video calling counterpart to Allo, is sticking around. Today the company announced an easier way to send video messages to your contacts.
As for Hangouts, the venerable chat app that launched with Google+, the company basically confirmed it would go away at some point last week, with users being "upgraded" to the Hangouts Chat and Hangouts Meet services now available for businesses.
Following the footsteps of a certain fruit-based competitor, Google is putting all their eggs in the Android Messages basket. We don't know how these enterprise apps will change to accommodate regular users, but we'll know more when the time comes for Google to kill off Hangouts Classic. We know that's happening, we just don't know when. Some users are unable to "heart" posts while others are experiencing issues with undelivered messages.