preview of next episode; next-time preview
Commonly used for the short preview shown at the end of a TV show, anime, podcast, or similar serialized media, teasing the next installment.
A preview of the next episode played at the end of the anime.
After seeing the next-episode preview, I can't wait for next week.
予告編 is a general trailer or preview, often for movies or longer works, while 次回予告 specifically refers to the preview of the very next episode in a series.
Compound of 次回 (next time, next episode) and 予告 (advance notice, preview).