The closer we get to the end of year, the more camouflage is peeled off the next-generation BMW Z4 that is planned to be officially revealed at next January's 2009 North American International Auto Show in Detroit. In these latest spy shots, the Z4 is only wearing bits and pieces of BMW's psychedelic adhesive plastic on its body while as you can see in the photos after the jump, the interior is as clean as it gets.

The minimal exterior camouflage allows us to get a better view of the 2009 Z4's two-piece retractable hardtop that eliminates the need for a fixed-roof coupe variant in the Z4's future lineup. But we wouldn't be surprised if the Bavarian automaker follows in the footsteps of Mazda and its latest MX-5 / Miata Roadster by offering a soft top version alongside the coupe-convertible seen in these scoop photos.

While the overall styling and sexy proportions of the current Z4 have been carried over more or less on the new generation model, BMW's designers have left out the fussy detailing of the original Bangle model which is a good thing in our books.

Same goes for the interior which follows the same architecture as before though it appears that the dashboard has a more upscale feeling. Other than that, the Z4 will benefit from BMW's latest iteration of the iDrive that was first introduced in the new 7-Series and the facelifted 3-Series Sedan and Touring models.

The new Z4's engine lineup will welcome for the first time, the Bavarian company's highly acclaimed 3.0-liter twin-turbo inline-six which delivers in its latest iteration in the 740i 326HP instead of 306 HP in the 335i. The range will also include 2.5- and 3.0-liter naturally aspirated six-cylinder engines while in most European countries the Z4 will be offered with an entry-level 2.0-liter 4-cylinder petrol engine.

The top-of-the line M Z4 model should arrive in the market by 2010 equipped with the M3's 420 HP 4.0-liter V8 unit.