The most logical answer is that it'll be a cover story about Egghead's characters, but there's a good chance that we could also have a break with random covers and then an Elbaf's cover story.
They don't necessarily come in a chronological order (e.g.: Gedatsu's cover story happened before the Baroque Works' one) and there were two cover stories themed after the same arc in the past (we also got an Enel's cover story), so it's possible that we'll have a Zou-themed cover story (the Tenure of Carrot, the Ruler of Zou?), a Levely-themed cover story (all the countries in trouble at the EoS?) or even something related to Moria/Perona (Revival of the Thriller Bark Pirates with Zombie Absalom?)... it depends on Oda's feelings at the time, I guess.