I always hesitate to tell people what to do with their stubs. But I'll tell you what I decided to do with the FoTF cards.
I had bought low on a handful when they were around 8k. As they've begun to climb, I off-loaded the ones eligible in the current event and held the others for now. I'll probably consider moving them if they rotate into active events.
Faces of the Franchise will be a part of collections. Every collection set provides a voucher for the bigger collections. And it's a virtual certainty that the cards will continue to increase. I personally decided to just take the profit now versus waiting and potentially being burned. If SDS is already adding Event Rewind packs, then there's nothing stopping them from releasing Rewind Boss packs and as I mentioned in the article - I think they will sooner than later.
So really it comes down to your priority. I'm not interested in finishing the Live Series stuff anytime soon but I still took the profits on some of these now. If you want the LS done ASAP, then taking the profit and moving on might be best. If you'd prefer to be ready for collections, holding onto them for now will do one of two things: provide you the cards to collect if those collections interest you or provide significant stub boosts if the collection doesn't interest you.
I'll just caution you (and everyone) that with the programs being different, the marketplace changes (quicksell values) and Rewind packs already floating around; there's really no way to know what the best decisions are.
It's ultimately why I am such a big fan of the changes. The last several years have been rinse and repeat. Buying event/BR/WS cards low then flipping them when the collections drop and ending up with millions of stubs and the collection done. That isn't to say this won't still be a thing, but it feels like SDS is intentionally trying to change the dynamic so I think we're all gonna slowly find out how the market adjusts.