BMW suggests that the next-generation models to their current line-up will get an evolved styling treatment and there will be better differentiation between models. Successors to the 1, 3, 5 and 7 series will have much more visual changes on the new models when they arrive.
As of date, the 3-Series and the 5-Series share quite a few similar design elements. The front end too has become very repetitive and does not have any major styling highlight off late. The company plans to use the headlights for better differentiation in the future. For example, LED headlamps in higher end models.
Also, Mercedes-Benz has been currently winning a lot of fanbase with their new, and younger looking design language. BMW wants to address this change from its arch rivals and does not want to lose sales to fresher looking models from the competition.