Not sure where to post this, but maybe Solo rather than TLJ where I put it before:
KK will be around for a few years to come. She'll oversee Episode 9 and assist with the introduction of the streaming platform. Assume that the KK era starts with TFA and ends with Episode 9 - there's four financial successes (Episode 9 will still rake it in) and one flop which is a pretty good tenure.
Using Palpatine foreseeing skills:
From 2020-2023 there'll be a transition period where the reins will be given to someone else, where the streaming service fills the void with a new animated series and live action features before a new cinematic trilogy begins in 2023. This trilogy will be released in 2023, 2025 and 2027 (the third instalment coinciding with the 50th anniversary of ANH for those sweet marketing dollars).