Google plans to kill Google Voice in coming months, integrate features into Hangouts | 9to5Google

Some carriers are probably worried that Google will, by consolidating its communications capabilities in Google+ Hangouts, make the services it's already offering more comprehensible and compelling to mobile device users...

"We’ve heard that Google Voice is getting dragged to the trash can and most of its functionality will be incorporated into the G+ Hangouts apps on both Android and iOS. This has already happened to an extent with the ability to phone friends on Hangouts, but we’re hearing the full shuttering and depreciation of the app is the next step.
What’s interesting here is that VoIP-to-phones is expected to be integrated into the Hangouts iOS and Android apps so that, just like with the Web version, you could be able to actually make (and receive) VoIP calls directly from your Google phone number. Whether the carriers and Apple are okay with this isn’t certain, and the thought is that it could be enabled by carrier like Apple’s FaceTime (or could be scrapped altogether) depending on the global market and the carrier."

Google plans to kill Google Voice in coming months, integrate features into Hangouts | 9to5Google