OK, here's way too much information...
Rooms By Category (total 875 rooms)
1=2
2=2
3=18
4=80
5=114
6=138
7=30
8=60
9=175
10=96
11=147
12=13
(BTW - I looked at the deck layouts and counted the rooms by Deck and Category - yea, that was a slow day at work

)
So if you are in a ...
cat 12 there are 862 rooms to upgrade to
cat 11 there are 715 rooms to upgrade to
cat 10 there are 619 rooms to upgrade to
cat 9 there are 444 rooms to upgrade to
cat 8 there are 384 rooms to upgrade to
cat 7 there are 354 rooms to upgrade to
cat 6 there are 216 rooms to upgrade to
cat 5 there are 102 rooms to upgrade to
cat 4 there are 22 rooms to upgrade to
cat 3 there are 4 rooms to upgrade to
cat 2 there are 2 rooms to upgrade to
cat 1 there is no where for you to be upgraded too
Now if you want to eliminate the "sister" categories where the "only" difference is the LOCATION your upgrade possibilities are...
cat 12 to 10 or higher: 715 rooms
cat 11 to 10 or higher: 715 rooms
cat 10 to 9 or higher: 619 rooms
cat 9 to 7 or higher: 384 rooms
cat 8 to 7 or higher: 384 rooms
cat 7 to 6 or higher: 354 rooms
cat 6 to 4 or higher: 102 rooms
cat 5 to 4 or higher: 102 rooms
cat 4 to 3 or higher: 22 rooms
cat 3 to 2 or higher: 4 rooms
cat 2 to 1 only 2 rooms available (the only place you have to go from here)
cat 1 sorry, you're at the top of the room higherarchy