The thing about booking a GTY is to pick a cabin category that you
will be happy with in case there is no upgrade. Most GTY cabins
are assigned around 50 days out from the sailing. So if you check
your Reservation on Carnival's website, it will tell you the cabin
number assigned. If it has not been assigned, it will say
TBA.
So far I have been lucky and have been upgraded the
majority of the times. But now that Carnival no longer allows the
Military discount with GTY cabins, I will have to start booking
assigned cabins.
Dave