Apparently the CLK 350 and the CLK 500 where not that different for customers, obviously the extra 25kw of power, extra 110Nm of Torque and more standard equipment didn't please those who paid the extra $26,000.
Consequently, Mercedes decided that the CLK 500 is no more, and in its place will come the CLK 550 as of 2007 (this is not confirmed yet for Australia since the range topping CLK 63 AMG doesn't exist in Australia, yet).
The CLK 550 will be powered by the same engine that the AMG CLK 55 is powered by, in Europe Mercedes offers the CLK 63, which is powered by a 6.3 Litre V8 that produces 354kw! We haven't got this car in Australia yet. However if Mercedes decides to bring the CLK 550 to Australia next year (or in 2008) there is a good chance that not only will get we get the CLK 550 but we will also get the AMG tuned monster, the CLK 63 AMG!
To be honest, Mercedes has so far kept the name for the new 5.5L version as Mercedes Benz CLK 500, instead of 550! I am simply guessing that once released, Mercedes will actually change its name to the Mercedes Benz CLK 550 as the numbers generally stand for the engine size (so the CLK 500 is powered by a 5L engine while the CLK 550 is powered by a 5.5L engine).