Android users have often relied on third-party SMS applications since Google's native app supplied with their OS has been far than ideal for most. In an effort to change this, Google has released a new app dubbed ‘Messenger' via Google Play earlier this morning. Not to be confused with Facebook's Messenger, Google's iteration focuses on SMS and MMS with support for both group and audio messages.
Messenger will be pre-installed on devices that are ship with Android Lollipop, but existing users with devices running Android 4.1 or later can download it via Google Play.
Does this mean the end of Hangouts? No, not entirely. They will be continuing to include and support Hangouts for the foreseeable future although I'm unsure why anyone would want to rely on it as their primary app for SMS and MMS purposes.
Source: Google Play