It depends on whether or not the BD player lets you split the audio when an HDMI cable is connected to the HDTV directly. On some players, HDMI to the HDTV gives you the video, while an additional digital optical cable connected to a surround system would provide audio. YMMV, according to model & feature set.
In this sense, yes, you should have the component RGB cables there if needed. Just buy them with a return option, like you could through Amazon, etc.