There is a rumor going around the blogosphere that Google may be working on a VoIP service utilizing Google Voice integration with Gmail. A spokesperson for Google tells WebPronews, "We're always testing new features and looking for ways to improve our products. We have nothing to announce at this time."
Google Operating System (an unofficial blog with "news and tips about Google") says, "Google tests a new feature that makes Gmail chat more useful: users are able to make and receive Google Voice calls from Gmail. A new phone icon opens a Gmail chat window with a dialpad, an option to find contacts, a credit balance and a call button."
The report adds, "The new feature will allow users to make voice calls over the Internet and it's likely that it won't be limited to Gmail."
But, as Google says, there is nothing to announce at this time, and they are indeed always testing features. Some of them come to fruition, and some of them don't. We'll have to wait and see.
Google did make video chat, voice chat, and group chat features much more prominent in Gmail this week.