Perhaps breaking the season into two segments of five episodes will allow the team more breathing room for production and promotion, and will eventually result in more consistent episode releases in the show’s future.
We can only speculate on when Rick and Morty will return, but it would make sense if the show returns later in 2020 than January.
This show takes a long time to develop, from the writing to the animation, so cranking out the entire season in the span of 3 months on television can make two years of hard work fly out the door pretty fast.