That depends on how much you're hanging your hopes on getting the upgrade. Upgrades are few and far between, and if you're counting on it, you're setting yourself up for disappointment.
Booking a category guarantee does not necessarily give you a better chance of being upgraded. What you'll most likely end up doing is paying $200 extra for a category 9 room when what you have booked, the secret porthole room, is essentially a category 8.
I think it's fair to say that you're just as likely to be upgraded from the secret porthole room than when booking a cat. 9 guarantee. Which is to say in either case, not very likely.