There is a lot of confusion on this topic.  I called Ford's customer tech support 800 392-3673 and I trust it is the definitive answer.  According to their tech support people, "MyTouch is not upgradable at the dealership level."  So as of now one can not buy a 2011 Edge or MKX and add the navigation later.  Seems like a mistake in the design but it is what it is...at least for now.