The Future of Fortune Scraps!
Cash them in, 10 at a time, for Zephyr Supply Boxes.
Open the boxes to get recipes.
Use, Sell, or Hold (and later sell) the recipes.
My guess is that they will likely make a return at a later date (the Sanctum and some of it’s related content) but it is so easy to get the scraps I wouldn’t hold on to them (unless they wind up in the new currency wallet).
I doubt they’ll be used for any other skins besides the current ones, unless Zephyr Sanctum returns next year and brings new rewards. Which it might, hard to say for sure, though the BotFW page did mention it was an annual thing.
Its not “now or never” though. The skins will remain available through the Black Lion Weapon Specialist in Lion’s Arch forever, so if you decide to keep them you’d always be able to decide to turn them in for some of those anytime in the future. Who knows, maybe you’ll make a new character that the items fit better or find a piece of armor they compliment well.