Khosrau II was, by all accounts I've ever read, an awful king and a very unpleasant character. It isn't out of the question that he might find himself overthrown earlier, to the great advantage of Persia, Rome and both their Arabian allies (depending on when the overthrow happens, it could butterfly the Islamic conquest of Arabia). I have difficulty seeing a different dynasty taking over though... Perhaps if Smbat IV Bagratuni, after successfully defeating the Hephthalites decides to make a try for the Persian throne and succeeds. That would result in a Persia with an Armenian Christian king. Could be very interesting...
fasquardon