As an avid user of both Google Hangouts and Google Voice, I would love to see the two services come together into one, but only if I do not lose my data and functionality from the Voice side. Well according to 9to5Google this exact thing will be happening in the coming months. When Hangouts was rumored and then launched last year at Google I/O the idea of combining all of Google’s different messaging services combining into one became a real probability. Since its release, Hangouts has replaced Google+ Messenger, Google Talk, and SMS functionality on stock Android devices. The only service left is Google Voice.
Google Voice has been a challenge when it comes to integrating it into Hangouts because the service itself offers the user their own phone number which people can text and call with over VOIP. This causes an issue when it comes to working with Hangouts because it is already pulling texts from the phone number that is associated with your phone/SIM card.
We have no idea when or how Google will bring the two applications together but it would makes sense if they did it around the time of when Google I/O 2014 is scheduled. All we can hope for is that Google does their usual thing and making services like these even better with every update.
Source | 9to5Google