It's possible that this will just be an "introduction of the game to the japanese audience". They'll get a trailer with characters that appeal more to them(PaRappa, Toro, Spike, Raiden, etc), and we might get a new stage or two... maybe they'll formerly reveal minions.
But that would explain the lack of leaks... Usually it's only characters that are leaked. :/
I think the op is trying to say that even know there is more characters there's a chance they might not be revealed at TGS. However the chances are high as TGS is one of the biggest gaming conventions of the year
All I know is, it would be strange to have FOUR reveals at gamescom, but 0-2 at TGS. TGS has been around much longer, and has been more significant.
Superbot works in mysterious ways.