If I'm following, you shouldn't have a problem if you purchase a Quarq, and later upgrade your bike...assuming that the crankset you go with for the quarq makes a compatible bottom bracket to the frame. There may be a few instances where that might be an issue, but for the most part you should be fine, especially if you are looking for something Shimano compatible. The Rotor 3D is Shimano compatible and looks schweet!