Not too long ago Google updated the desktop user interface for the Hangouts for Chrome app, which left people wondering when Google would get around to bringing the UI current for the Android version of the app as well. There is still no exact time frame for when that may be, but version 4.0 of the Hangouts app, which will be the next version to hit smartphones and tablets, seems to be popping up for users to grab a quick glance at what's coming. This includes some obvious UI design changes as well as some overall restructuring of the application to provide a more streamlined look and feel.
As of now Hangouts has a little bit of material design going on, but it isn't 100% of the way there. In version 4.0 Google will change things up a bit more and add things to make the design more current with other material design styled apps. Google of course still has time to change some things as the screenshots provided by Android Police are early looks. What is perhaps the most noticeable is the presence of the floating action button in the new version of the app for initiating new conversations. Other slight, yet still noticeable changes see the "+" button in the top right corner being replaced by the overflow menu button (the three dots), and there is now only one tab for the main screen (unless you have Hangouts Dialer installed on the device) when you open Hangouts which displays you're currently running conversations.
The header bar has been thinned out a bit and is no longer as deep as it is currently, and the name of the Google account which you're using Hangouts with has been replaced with the app name. Contacts have also been moved, as they now sit in the hamburger menu, however, Google has also made it possible to access your contacts by pressing on the floating action button as well, which will list options for new conversations, new video call, new groups, or options for picking any one of the conversations which are already open.
Other visual changes include swapping the color of the incoming and outgoing messages, where incoming messages now appear green, as well as updating the shade of green to match the color of the Hangouts header and overall color scheme. Google is finally going to be implementing status capabilities within the Hangouts app it looks like, which will make it possible for users to change their status through the Android app as well now. Google is tweaking the layouts for the attachments too, along with a more material design like button for inserting the attachments (i.e. stickers, emojis, photos, etc.) when you have one selected. For users who have Hangouts as their default SMS app, Google is making it easier to switch back and forth between messaging through your Google Voice number or your carrier number with a drop-down menu in the message box, although this is not too different from the way it is now. Overall there looks to be a few much-needed overhauls while mostly the update looks to be about refining the overall design, but expect there to be some improvements and bug fixes as well.