Do you mean UN-FIXED used 2015 ?
... guess there might be another way for owners of new-ish 2015(s) to sell to the public ... that is IF the buy back is cheap-ish

At this point ... all my options are open... with my 2015 low mileage Golf
(1) FIX ... and take the $$$$
(2) Buy back ... if it is a good settlement
(3) Sell to private party ... if it is better than option one or two
NO, get it FIXED & collect your Generous Compensation.
What I mean is, the "FIX" on 2nd & 3rd Generation TDI's is going to be very minor, probably nothing more than an ECU Software Update. This is NOTHING!
There will be aftermarket flash updates for sale all over the internet offering flashes back to original probably the very next day after the "FIX" details are released. Or better yet people will get performance tunes & make their cars more powerful with better MPG than they have now even before any "fix".
Sure there are going to be a small group of people who bought 2nd & 3rd Gen TDI's based on the whole green car aspect, they can just take the buyback & be done with it for good. Go buy yourself an electric car with the money, or ride a bicycle if it bothers you that much.
People who own and love the latest model years in best condition low miles
1st Generation TDI's are going take the biggest hit from all this, their options may very well be:
Sorry, no fix available & be forced into buyback (at least in California For Sure they will block registration FOR SURE)
OR WORSE, the "FIX" on 1st generation cars may be to cut it full of holes and have MONKEYS hack in an afterthought BS SCR System. That's the WORST THING you could do IMO as resale value on such a vehicle will be in the gutters, & no way is anyone doing that to a car I still own, so it's FORCED BUYBACK option no matter if I like it or not.
TDI owner friends of mine OUTSIDE CALIFORNIA say they're not going to do a damn thing. Well, they may or may be OK, we don't know for sure what may happen, if enough of them take this stance, who knows.... they may block registration of vin numbers for all 1st generation TDI's Nationwide.
Also, they wouldn't get their "Generous Compensation", GENEROUS COMPENSATION is there so owners will either get their cars fixed, or sell them back to get them off the road.
In any event, 2nd & 3rd Gen TDI's have lots to gain (FREE $$$) & little to loose, it's owners of the best condition low miles 1st Generation TDI's that will loose the biggest IMO.
Owners of HIGH MILE 1st Generation Beaters make out like bandits too.