"What I will say is of utmost importance. As many already know, the game's development has lagged significantly in recent months and despite our efforts, the date of the next release is becoming increasingly remote. :/
The main reason for this delay is due to the large amount of missing animations, and the short time our Spriters have to finish their work.
We can't push our Team members, because they have decided to give us a little time to help with this project without receiving anything in return.
Because of this delay, Zeta and I have decided to create a development plan with which we hope to speed things up:
Step 1 - To lighten the animation work, we will temporarily remove several playable characters. During the upcoming releases will be only Zeta, Zu, Rouge and Tails.
Step 2 - When we finish Stage 5, we will complete the missing characters: Amy, Blaze and Cream.
Step 3 - After Stage 5, we will repeat the first step of the plan. Only used four playable character to fast forward the Stages 6, 7 and 8. Thus, we can complete the whole game. ^^
Step 4 - Now with the game complete, the final step will be end with the missing characters. From this point, we can add new characters, which will appear in future versions.
I hope this plan can help to accelerate the development process.
I know many will not be happy with the temporary absence of some characters, but it's all we can do to release updates more frequently.
I hope you understand and sorry for the delay.
Thank you."
As explained by Neoeclipse and spoilered due to it's length