It certainly seems from the outset like this will be another net negative for QFF members, particularly those with meaningful status that lose some of their inside track on upgrades, but I also think we need to wait and see how expensive these are before getting into a panic about it.
This is not like 'Bid Now' upgrades, where sometimes quite low offers, using points as a payment method might be accepted for a last-minute upgrade; these are confirmed paid upgrades - something as others noted have always been possible to call up and secure at any point, but people rarely do it as it's generally more expensive than having bought a Y+/ J / F ticket outright in the first place.
If you had the money to do it, would you not have done that at the beginning? Circumstances changed? Saved up some more since ticketing? Maybe. There's also the business travellers on a Y or Y+ travel policy who self-fund upgrades, but I do think it's a relatively tough sell when there is no additional status credits over the original fare.
Again - it will all come down to the price and how it compares to paid cabin class upgrades today. I chance nothing and book the cabin I want to travel in, but I'm looking forward to seeing the kinds of offers they put out there, and how often they appear.
Cheers,
Matt.