As a Full Member I got 100 merits, and have to go to 250 to get Senior Member, a 2.5 multiplier, I applied it here, Legendary is 1000, Mythical (or whatever) would be 2500.
So you used two data points (Full Member/Senior Member) when you could have used
three (250, 500, 1000). It's very likely the next number will be 2000.
So tell me, how many members have 2000 merit? Only one - Theymos.
Is he going to introduce a group to make himself the exclusive member and infer that we are not as good as him?

I would predict that a new group will not be announced until there are several/many members in it. So I wouldn't hold your breath.