Some things I'm hoping to see:
Bigger roles for the MCPD and Mixies than in EKHID
All (or at least some) the Mixels from Series 1-6 showing up to participate in the action, like in QFM
Some new, gigantic, supereffective Nixel plan that almost destroys Mixopolis (kind of like QFM, but the destruction is happening the whole time)
Equal focus on all the characters (even if most do nothing, at least they do nothing together.) I also think there will be a lot more focus on the tribes as opposed to individual characters.
Some Mixtical thing that either destroys or neutralizes the Nixels forever (as opposed to the Ultra- Miximum Max, which just made them retreat)
An all-out battle featuring every character for the future of Mixelkind itself (big confusing battle is big and confusing)
I imagine it will also be a lot darker and more destructive than any of the previous episodes.