The blogosphere is abuzz about Google’s plans to integrate a “Twitter-Killer” into GMail – and there are already people such as Robert Scoble boldly suggesting it’s not going to happen.

Twitter is the dominant micro-blogging service, having forced Pownce (remember them?) to go away while a score of such as StatusNet and Plurk quietly toil away in the background. Meanwhile, Google’s first stab at the market, Jaiku, was a dismal failure.

That said, anyone who dismisses Google’s chances of posing a threat Twitter would be making a mistake. Here’s a few reasons:

1. Despite Twitters’ large user base – 50 million or so around the world – it’s growth appears to be slowing, particularly in the U.S. where it has been flat in recent months. This may suggest that Twitter as a standalone service has reached a saturation point.

2. GMail’s popularity provides Google with a huge potential market to launch a Twitter-Killer. GMail users are already are used to having conversations using GTalk so adding another feature is not coming out of left field.

3. GMail is also a excellent demonstration of how Google has bene able to break into new markets. At the time, Hotmail and Yahoo Mail dominated the landscape, so GMail received a tepid response. Today, it’s one of the most popular e-mail services.

The keys for Google’s Twitter-Killer will be how well it is integrated into GMail, and the features it offers given Twitter’s weak spot is the fact it continues to be a no-frills service.