Here's the list of all monsters slated to challenge Godzilla for the title King of All Monsters in the next and final movie:
King Caesar
Minya
Ebirah
Kamakaris
Kumunga
Gorosaurus
Manda
Gigan
Angilas
Rodan
King Ghidora
Mothra in Larva Form
Monster X
and of course, Godzilla...
(what, no mecha-kaiju?!?!?!)
Source:
www.henshinonline.com by way of
www.kfccinema.com