The 5D Mark II was announced in October, 2008. So, the sensor is getting long in the tooth. However, it still takes just a beautiful image today as it did the day it was released. And, same with the original 5D.
It's quite telling that the gap was quite small in release dates between the 5D Mark III and the 6D, and the 6D performs better in terms of noise characteristics. So, even in those few months, there was advancement in sensor technology.
Oh, there's also rumours of a 40 megapixel monster around the corner, too.
I think I might just have to get one.
H