There are rumors of a lighter-weight/more-naked version of the new K1600, but nothing at all firm. Sales of R versions of bikes haven't been particularly good for the last few models, so I would doubt anything is in the pipe for the near future. OTOH, it would be rare for BMW to develop an engine for only a single model. So who knows?
BTW, I have a very nice 79 CBX and while it is a good bike and super cool, a six-cyl by itself doesn't guarantee more smoothness than a carefully setup four with balance shafts. The K1200LT was an extremely smooth bike so we're definitely getting into an area of marginal and diminishing returns. I think BMW could have met their design goals with a big four, but needed to match and surpass the class-leading Wing which has a six.
Last edited by markjenn; 10-08-2010 at 02:23 PM.