I wouldn’t bother trying to predict the crowds. Galaxy’s Edge’s impact is a huge unknown, as well as 2021’s 50th with the slew of new attractions on the way.
I personally don’t think the Galaxy’s Edge opening can really be compared to Pandora’s. Star Wars has been around for 40 years — and over time has built a fiercely loyal and engaged fan base of all ages. And there’s very wide appeal beyond the super fans. I really doubt GE crowds will be that much lower in 2021, but there’s really no way to know.
I would just go when you want to go. If you want to go sooner, I’d do it. If you want to wait until more new attractions are open, I’d do that.