On reimbursement of costs for enforcement actions & related issues

I find myself inspired to quote Futurama: You are technically correct! The best kind of correct!. Yes, indeed, under GPLv2§4, the violator will lose their distribution rights (read more in Copyleft Guide), and that termination relates to any copyrights infringed in the original product. Thus, indeed, if those copyrights are redistributed in a later product, their rights have already been terminated.

But, this is where I again have to say that the GPL isn't magic pixie dust that just works. If the violator doesn't wish to comply, we have to compel them somehow. Termination of rights works the same way as it did in the first product, and has the same tools available. Namely, we can go into court, and seek an injunction; just like we'd have needed to for the first product. The fact that the rights terminated long ago in past product might help us convince the judge to grant an injunction more quickly, and/or show the judge the company acted in bad faith. But, the enforcement process is the same, and note that one way to come into compliance is to stop distributing. Therefore, with regard to the old violation, the company is now in compliance. We're unlikely to therefore get a judge to compel a source release for the old product, since distribution has ceased.

First, it's worth noting that Conservancy doesn't just represent a coalition of stakeholders (although we do that too), but Conservancy is also a copyright holder in Linux as well, as some stakeholders have outright assigned Linux copyrights to Conservancy. But, that wasn't your question. To answer your question: Yes, you're quite correct about how rights restoration works (at least in the USA and most other jurisdictions I'm familiar with). The negotiation point that both FSF and Conservancy use in that enforcement scenario is simply tell violators that once compliance is achieved, we're on their side and prepared to be an expert witness or otherwise help the former violator oppose any copyright holders knocking at the door for huge settlements. Such copyright holders who came to demand pay-outs after compliance was achieved of course wouldn't be acting under the principles of ethical GPL enforcement anyway.