If Rosalina is a host, then Mario Party with Super Mario Galaxy theme suits well for her... but I want her as a playable character.
Koopa and Shy Guy... they both can be the host, but I expect them as a playable character.
If Count Bleck or Shadow Queen is a host, then I guess it will be a Paper Mario Party. But I think they won't fit since they are villains.
I don't know who fits for the MP9 host... but I'm guessing it will be a new Mario character.