I'm guessing it's a secret. Since the Master said he wanted to pick Laxus and that Garjeel was off doing something, but their both on that team so...surprise their enemies maybe?
Anyway, since Jellal isn't in prison it's pretty obvious he's going to be the new Mystrogan.
I was thinking that they would pretend to "quit" FT and therefore be eligible as being another team, but the council (or whoever is running the thing) shouldn't be that dumb to buy it.
I'm really hoping it's actually Mystogan there and not Jellal in disguise, but I think you're right.
If it's not Isuzu-chan Mii~