If Cathay is worried about late cheap upgrade is going to discouraged premium flyers, or make premium-flyers buy cheaper Econ tickets and waiting to upgrade on the spot, then they are as wrong as thinking the new MPO 2.0 will bring back high revenue premium flyers that will more than compensate for losing mid-level Economy flyers.
The fact of the matter is most premium flying customers are paid by their company. These guys will be just as cheap as your Q-fare flyers when they are traveling on their own dime. Offering low-bid last minute upgrades on your empty premium seats will not offend these premium-paying flyers away (ignore all the threats on the forums such as this one), and will not discourage out-of-pocket paying C-class flyers (such as myself) from buying cheap Econ fare and wait till last minute upgrade. Why not? Because I don't want the risk of the flight being full and not being able to get a C-seat. If I have to have a C seat, I pay for it (reasonable D, I fare).
I have talked to management of MU and 3U that do offer last minute cheap upgrades to their C class, and they say they never had a problem selling C class seats straight-up, and it's actually becoming rarer for seats to be available for last minute upgrade.
Cathay is losing people in C class on other reasons. Enhance 2.0 isn't one of them.