I honestly doubt he meant it. He was trying to hype up the manga and not reveal his plans. No writer would bring in a villain with knowing how to kill him. Especially not a writer who's been doing this for more than 10 years. Unless Kishi is a rare gem.
1)Double Kamui Obito would have send Madara to Kamuiland.
2)Sakura could have just destroyed his eye.
3)He could have had Gai killed him with that last attack, like Madara said it could.
4)Naruto and Sasuke could have sealed him the moment he was teleported between them. Instead of hitting him with Rasengan and Chidori.
5)Naruto could have took him down with all the natural energy on the planet. With Sasuke's help.
The list goes on.
