You know how some things are just inevitable? Like, a plant will wither if it doesn't have an adequate amount of sunlight and water? That's kind of what's happening Google Voice, if the latest hearsay is to be believed.
9to5Google reports from its own unnamed sources that Google plans to do the inevitable: roll up its Voice functionality into the Google+ Hangouts app for both Android and iOS devices. Hangouts will be able to do VoIP calls and SMS via your Google Voice number, in addition to the video calls and instant messaging it's capable of now.
It all makes perfect sense: once sequestered as its own standalone app, SMS messaging integration was recently rolled up into Hangouts after the launch of KitKat in an effort to kickstart Google's idea of a unified messaging app. Google Talk and Google Plus instant messaging are also a part of that package, and every service is easily accessible through one unified Omnibar that lets you search for anyone, whether they're in your Contacts or a public Google+ user.
Also consider Google's insistence for its users to use Google+. The social network is slowly transforming into a portal for every Google service you utilize. All the Google things that are not tied to a Google+ account are slowly being swallowed up by the things that do.
None of this is a new concept, but rather the proper evolution of Google's myriad of services. Its competitors, Apple and Microsoft, both insist you have a user ID to log into its services. Both companies also offer their own unified messaging portals: Apple's Messages on the Mac and iOS, and Microsoft's Lync on the desktop.
Either Google will push forth a silent update for Hangouts—as the company is known to do with some of its high profile services and apps—or we'll expect to hear an official announcement during the Google I/O keynote. For now it's just an unconfirmed rumor—and a wish that Google would just pull the trigger on the inevitable.