It is not a secret anymore – BMW is in the middle of developing a 4×4 Coupe named X 6 based on its big off roader X 5.

Now here is another prototype mule suggesting what is up next. Since BMW has been very successful with the current X model line- up consisting of X 5 and X 3, it is very likely that now the smaller 4×4 model X 3 could become the base for another crossover coupe, the X 4.

As can be seen on the photos, the test car is an X 3 but is longer and wider, and it runs on sporty wheels. For the time being nothing has leaked through about the styling , but it can be expected that this model will bear some resemblance to the upcoming X 6.

While the next generation X 3 is scheduled for release in 2010, a matching SUV Coupe X 4 could be due at about the same time.