App developers must stop making unauthorized use of Google Voice by May 14, 2014
Starting with the launch of the Nexus 5, Hangouts will integrate seamlessly with your SMS messages. That is, unless you're a Google Voice user — always a bridesmaid and never a bride, Google Voice is getting left out in the cold again with the latest Hangouts update. Google has confirmed that you'll only be able to use SMS in Hangouts v2 through your regular carrier number, but rest assured that it plans to bring Google Voice support soon.
The plan is to have Google Voice integrated into Hangouts "by early next year," citing that there are obvious carrier hurdles to making it all work. Additionally, work is being done to bring Google Voice numbers to international users as well as support MMS. While we wish there was a clearer time frame for how quickly Google Voice users can be brought up to speed, we'll never turn down some reassurance that the feature integration is coming.
Going further, Google Voice is going to get notably more secure with changes to the ways third-party apps have access to the service. Developers who currently violate the Google Voice Terms of Service are being notified of the upcoming changes, and have until May 14th, 2014 to remove the offending apps or transition users to a new system.
Source: +Nikhyl Singhal