Management of obsolete software- and hardware-components along with the addition of new components and functionalities in existing embedded systems can be a very difficult or almost impossible task. If there at the same time is a requirement put on the system that it should be in operation for more than 30 years, then the evolution of the embedded system architecture over such a long duration of time will be an even more challenging problem to solve. A large number of different industries, for example the process and power transmission industries, are faced with this type of challenges on a daily basis. The contribution of our research presented in this paper is a set of questions and answers on how it is possible to replace and update an old control system, with examples inherent in process and power transmission applications. We also look at different methods that can be used during the development of new systems such that they will provide a natural support for evolvability, targeting future control system applications.