My recollection from what I've read on this thread is of no one reporting success with the following situation (new reservation at a previously reserved property that has increased 2 or more categories about the old to new cat mapping - and one doesn't have a Points Advanced reservation locked in), but just wanted to check before I call:

One of my old certificates is OC9. It is currently attached to a reservation but I cannot make those dates, and I am about to call to detach the certificate. The OC9 maps to a new cat 6, but the property is now a NC8. In an ideal world I thought it would be nice to pay the points difference from NC6 to NC8 and make a new reservation at that property (and frankly granting such requests, ime, is the way Marriott Rewards use to be before last year's massive devaluation and new less friendly customer policies). Unfortunately, this now a 2 category upgrade that would be required to reserve the very same property.

If I call do I have a significantly > 0% chance of getting such an upgrade approved if I have my new reservation dates ready?