Here is how Megatron's plot and Yuna excepted the wager goes in The Journey Back to Life Part 2.
Quickstrike: That went well.
Megatron: But, With Princess Yuna out of the way, No one else will interfere with our evil plan. Yes!
Quickstrike: What's gonna happen now, Boss?
Megatron: Quickstrike, You are now partnered with Scorponok.
Scorponok: So, What's your plan now, Megatron.
Megatron: It's time we take over every kingdom of Equestria one by one. Starting with Canterlot!
Predacons: (evilly laughs)
In the Land of the Remembered.
Princess Yuna: I'll except the wager, If you keep your word.
Xibalba: Of course, Princess. (stick out his hand) Do we have a deal?
Doc Hudson: Is she going to do it?
Emperor Lunarlight: We'll find out.
Princess Yuna: (stick out her hoof) Deal.
The Candle Maker: Let the challenge begins.
Tadashi Hamada: Good luck.
Princess Yuna: Thanks, Tadashi.