Here's why:
* Rick Riordan hasn't announced a sequel series: While he has confirmed the Trials of Apollo series is finished, and that he has ideas for the future, he has not confirmed a new series or the inclusion of a child for Percy and Annabeth.
* No official confirmation: There is no reliable information or insider knowledge about the next series that mentions a child for Percy and Annabeth.
* Fan theories and speculation: It's possible that fans have theorized about this idea, but it's crucial to distinguish between official information and fan speculation.
Remember: Until Rick Riordan or an official source announces it, any information about Percy and Annabeth having a child in the next series is purely speculation.