Thinking about Di2 and other e-shifters, and the frames designed to accommodate them. If one were to get a custom frame built around such a system, how much will obsolescence of the tech or changes in the mounting/routing change over the course of years? On a custom frame, one wants it to last a lifetime (or as long as possible), so what are the chances that a Di2-built bike will fail to accommodate a later incarnation? Or is the layout of the hardware pretty set in stone at this point?