The HPFP on a good many of these cars already has an extended warranty on it. (IIRC to 120,000 mi)
If you eventually have "the fix" done, the mandatory warranty for "the fix" includes the HPFP in which case you are good for another 48,000 mi.
The car has to be "operable" in order to qualify for the buyback ... which tells me, you are SOL if you have a HPFP failure and then ask VW to buy it back (because you will have to tow it to the dealer, it won't be "operable").
I refuse to buy any vehicle that has a Bosch CP4-series injection pump. Pretty much means no more diesels for me.