The BMW boxer motor has several design advantages, but they're not in use any more. Cylinders sticking into the wind for air cooling aren't needed when the motor is water cooled; 180 degree primary balance doesn't matter when you've got a balance shaft inside; low CG can now be obtained by leaning the cylinders of an inline 4 way over (and get even more weight on the front tire).
In the meantime, the disadvantages of a boxer motor are weighing ever more heavily: limited lean angle, which can only be fixed by moving the engine up in the frame, raising the CG; extra weight by having essentially completely separate cylinders and heads that can't share weight or components.
It is often said that the success of the original BMW motorcycle design was based on the fact that, more than any one component, it was designed a logical progression of pieces that worked together. The longitudinal boxer that allowed great cooling fit with the automotive style dry clutch and clean, reliable driveshaft. The double cradle frame on the original R32 didn't look like the bicycle frames that other manufacturers were adapting to motors.
I've never owned a BMW that wasn't a boxer, I really like them. But buidling a water cooled boxer doesn't make design sense, it only makes marketing sense.
If they're a good bike, however, I'll probably get one eventually (when I wear out my R12ST).