just wanna get this straight: is outworld defending it's realm from the dragon king? here's what i think is happening:

1.)after the dragon king takes over outworld, the outworld characters will escape to earth realm.

2.)then dragon king will try taking over the earth realm in mk7, where outworlders and earth realmers will unite to defeat him.

3.)the outworlders and earthrealmers combined strength will be enough to defeat dragon king.

4.)then, once dragon king is gone, they will turn on eachother and fight to gain control of earth realm (since outworld has been destroyed by dragon king) in mk8.

just my 3 cents of theory