I really think we are going to see a buy back here.
Any settlement that is approved by the parties (in the case of the owners, by the plaintiffs' committee) is going to designate a fund that will be large enough to pay all of the above. There wouldn't be any order of precedence because the fund would be enough for all. And if you as an owner are not satisfied with the deal that the plaintiffs' committee negotiates, you can opt out and sue yourself. Only bankruptcy would influence your eventual recovery in your private suit. The court isn't going to say, "too bad for you, VW already paid out $XX billion so no more for you."
I love the FTC suit. It's entirely consumer-oriented and it's purely equitable, so no legal relief (i.e. money damages) is relevant. VW can only take back the cars and disgorge its enrichment to the defrauded consumers. It's hard to see how a judge could order anything different given the admissions VW has already made, so it's hard to see how a buy-back/take-back could be avoided given this new suit.