All,
Ismay only got the B52/54/56 suite because on sailing day - April 10, 1912 - there were no paying passenger bookings for it (all have been cancelled). If Morgan was to sail, I assume and it is highly probable that Ismay would have occupied C62/64, which at the time of Titanic's sailing was not booked or occupied by anyone (no the Astors were not in this cabin).
Daniel.