It's certainly not very popular anymore, but there are still plenty of CM's willing to trade, and the occasional fellow guest. I'd say if you're into pin trading for the fun and camaraderie, it's still a thing you can do at WDW- I certainly did on our trip a couple of weeks ago, but mostly with CM's. If you're into pin trading from a collector standpoint- where you're interested in trading pins based on their respective value, or picky about what you trade- you probably won't have much luck; that scene appears to have moved to the internet. For the most part I let my 4-year-old decide what we would trade and what we were looking for, and the interactions were fun. We did trade with a few guests (mostly other kids) but for the most part it was resort and retail CMs, some of whom had boards rather than lanyards.