Hearty congratulations followed by the dark spectre of creeping doom for Microsoft today following news that the revamped Xbox 360 is a retail hit in the United States, but there’s not much mileage left in Microsoft’s popular home console.

According to Redmond-based Microsoft, its new streamlined Xbox 360 – which was unveiled during the recent E3 Expo in Los Angeles – is selling well in its home region ahead of the console’s retail arrival over the pond in the United Kingdom.

“We are hearing great feedback from retailers that the new Xbox 360 250GB is experiencing unprecedented demand,” trumpeted the software giant in an official statement.

“Consumers are eager to experience this new console, completely redesigned for the future of entertainment: sleeker, smaller, and whisper-quiet,” it added.

Yet, despite Microsoft’s vision of gaming hardware “redesigned for the future of entertainment,” industry analysts at DFC Intelligence are claiming that the Xbox 360 has already passed its retail peak and sales are expected to decline from here on out.

Offering up its projections in a Gamasutra report, DFC Intelligence contends that: “The Xbox 360 has some good years left, but the platform is clearly on the downside of its lifecycle.”

It also believes Microsoft’s new Kinect motion-control technology will fail to have a substantially positive effect on flagging hardware appeal and that Microsoft “is putting almost all its eggs into the Kinect [basket] as a way to appeal to the ‘casual’ consumer and expand its user base.”

When it comes to appraising Microsoft’s competition, DFC offers that sales of Sony’s PlayStation 3 console will continue to gather pace during 2010 and 2011, while the Nintendo Wii will lose momentum but remain the market leader.