Hello,
we cruised the MAGIC last August on the 7 day Western. Our GTY room info came with our cruise docs, but they arrived later than others sailing with us. I called several times, as I was impatient and was told the assignment of the GTY depended upon the category. The lower cats were assigned their upgraded GTY's earlier as the lower cats seem to be in bigger demand closer to cruise date.
We went from port hole room to a navigators verandah, and this did not happen until 2 wks prior to our sailing.
How true this is, I do not know.