I don't know actual dates, but 4 Points in Danang is very much under construction, as there is simply no interior to speak of (no walls enclosing it). The Grand Sheraton is this massive castle rising from the ocean and looks amazing at night, and I didn't go inside (cause you have to drive in their grand entrance) but it seems it may actually open soon.
There is no Sheraton Hoi An to speak of, as no recognizable building I saw.