There is zero chance of a suite upgrade from a cheap room. This hotel has an unbelievably high occupancy rate and huge numbers of VIP guests.

Standard upgrade for a Diamond from a base room is to the Exec floors or to corner rooms on other floors (since you get Exec lounge access anyway). On occasion I've received a Relaxation Room which is very nice. In line with the suite upgrade, do not expect one of these for a multi night stay,