I definitely don't think the 8+ people that joined the facebook group were waitlisters. Not at all. I haven't joined the groups of the schools I got admitted and I'm just not quick on joining groups. Some people join later, some people are accepted to the group by mods later.
I mean, let's not overanalyze the facebook group. I think we can compare the 450 members at the HBS group compared to 198...and even Duke's 168 members when the class size is half of Wharton's. But thinking the 8 people who joined in the last days were waitlisters? Lol, I don't think so.
I have a few friends on the WL too and haven't heard of any movement.
To be honest, I don't think there has been any movement as of yet. Just my opinion. I could be wrong.