In a recent panel at Dragon Con (Found below the break), the audience asked John de Lancie himself about his roles in the upcoming season 4.Some of the major points here:
- 4-5 episodes so far (meaning we have 1-2 Discord episodes on season 4)
- A Discord song is on it's way
If you want to check it out for yourself, you can find it below the break at the 34 minutes onward mark.
Thanks to Fluttershy_Z for the heads up!