Update: That was fast. Google has confirmed the feature will begin rolling out in the U.S. immediately. Besides being able to make free calls within the U.S. and Canada, or paid for other countries, you'll be able to receive calls. Incoming calls will pop up as a chat window in Gmail and ring your Google Voice-equipped phones simultaneously if you have one.
Google is reportedly in the process of testing a new Gmail feature that would allow users to make calls from within the service's chat interface. Gmail already supports voice and video chatting with other Google Talk users via a desktop client or from the webmail interface itself. However, the new feature appears to be the result of Google's Gizmo5 acquisition last year and will reportedly enable users to call mobile or landline phone numbers without the need of additional software.
The implications and motivations behind such a product should be obvious – a platform-agnostic competitor to Skype and other VoIP services that works with Google's forthcoming browser-centric Chrome OS. According to Cnet, the new feature's interface strongly resembles the one used in Google Voice but the two are separate from each other – at least at this point. This could mean that the new phone call service won't be limited to users in the U.S., though calls placed to U.S. or Canadian numbers will reportedly be free, with discounts on international calls as compared to standard rates.
Google Voice doesn't currently support VoIP calls. The service, which assigns you a free Google number that you can connect with all your active phone lines to have one universal number, finally opened its doors stateside back in June and there has been some speculation that it would eventually be merged with a VoIP client of some sort. It's unclear if this is a first step in that direction or if the integration will be limited to Gmail – if at all. A spokesperson for Google said that the company is always testing new products and services, and that it had "nothing specific to announce right now."