1. New lair. Maybe a buried spaceship like the one they found in Buried Secrets
2. More Mighty Mutanimals. Like Newtralizer, Mutagen Man, Karai, Mondo Gecko, Sir Malachi, maybe Splinter or Mikey (Turflytle)
3. More Splinter alone in New York. (With a return by Rat King)
4. The Invasion resolved in the season finale (with Shredder mutating)
5. Tokka appearing halfway through the season
What do you guys think?