I actually spoke to a manager about the upgrade when I had an issue with breakfast. According to him, they normally allocate elite members to the best available room on checkin. They do not normally reserve better rooms prior to checking in, which I was told. So if you check in late, it's quite likely that all better rooms are taken.

Btw, I booked a breakfast rate for this time, which excludes a cold drink. You can choose water, coffee or tea, and buffet or $10 off a la carte. Egg menus are not included in the buffet. I was quite surprised to learn that a glass of juice was charged. If I pay, I rather go out to a nice cafe.