To be honest, the gokage having secret techniques up their sleeves seems like bullshit at this point in time, even if it's something they have to prepare. After all the fight with Madara was pretty long. They could have covered each other while preparing it.
And if anyone should have a secret technique hidden I feel like it should be Gaara or Mei.
Still... Besides that it's a pretty good prediction.
Lol'd at Hiruzen getting buff xD