Nintendo usually ties a new mobile game to a new main console installment in that franchise. (gimmegimmegames.com)
If Wii Party had Miis, then there's no reason why the 9th console installment of Mario Party shouldn't include them since roughly the same people behind the success of Wii Party are indeed working on Mario Party 9. (mariopartylegacy.com)
Nintendo usually ties a new mobile game to a new main console installment in that franchise. (gimmegimmegames.com)