Nope, no idea. That would involve me using some sixth-sense to predict when the final entrant signed up! 
I'm not totally sure how the Tourney works - I'm hoping that, when I enter the names, it doesn't immediately throw people into their battles, but rather tells them it is time for their battle. That way a) people are able to meet equipment restrictions and/or hela up before actually starting and b) people aren't left waiting in the arena for their opponent.
If necessary, I might end up deleting the Tourney after creating it, waiting until everyone is ready, and then creating it again. I hope that isn't necessary, though.

I'm not totally sure how the Tourney works - I'm hoping that, when I enter the names, it doesn't immediately throw people into their battles, but rather tells them it is time for their battle. That way a) people are able to meet equipment restrictions and/or hela up before actually starting and b) people aren't left waiting in the arena for their opponent.
If necessary, I might end up deleting the Tourney after creating it, waiting until everyone is ready, and then creating it again. I hope that isn't necessary, though.