I just don't see "over-saturation" as some sort of long-term problem.
By the end of 2019 there will have been 12 Star Wars feature films (that includes the animated Clone Wars film) released since 1977. That's one released every 3.5 years. Total box office receipts of all 12 (not including special edition or re-release)? $8.483 billion
If we change the parameters and count from 1999 (Episode Uno) to 2019 (Episode Nueve) a period of 20 years in which 9 feature films were released, the frequency of release changes to one film released every 2.2 years. Total box office receipts of all 9? $6.986 billion
If we cut to the Disney era - from TFA in 2015 to Episode IX in 2019 there have been 6 films released. That's one film released every eight months. Total box office receipts of all 6? $4.445 billion
Clearly, an increase in frequency of release does not negatively impact receipts. In all fairness, SW's limited appeal to the Chinese marketplace may be the only easily apparent road block to continuing success.
Upcoming film projects include a Rian Johnson helmed trilogy (unknown release date) and the GoT dudes series (very unknown, with details not forthcoming until 2019 or later) - along with rumored one-off films like the Kenobi film, Boba Fett film, and a TV series on Disney's streaming service. We can think of those as "Phase II" but there is no indication that these films will "flood" the marketplace, and most likely they will remain in a two films or less per year pattern. Disney has been making bank since their acquisition, and they continue to integrate their property into their theme parks and other branded outlets. Disney's over all corporate strategy may make SW products more ubiquitous, but there is no indication that their film release strategy will somehow exhaust the story ideas of the SW universe or make it less appealing (to everyone but the Chinese of course).
Let's compare the SW franchise with the Marvel Cinematic Universe...
Over the past 10 years an astonishing 23(!) MCU films have been released... that's one every five months!
An additional 7 films are set to be released by the end of 2020 - which would make a total of 30 in 12 years - averaging about one every four months for a period of 12(!) years. There have also been 12 or so TV series as well, some cancelled, some ongoing.
The total box office receipts from the MCU films is $13.510 billion dollars. 9 of the top 10 MCU films (as far as box office receipts) have been released in the last 5 years, and 5 of the top 10 have been released in the past 2 years. So "franchise fatigue" has not yet affected the most franchisey of franchises.
It's difficult to see how a franchise like Star Wars, which is arguably more appealing globally than most of the MCU, has a far smaller presence on TV, and has a greater story potential (with the erasure of the Expanded Universe) and more instantly recognizable characters, would suffer from an increased release rate, or more TV series, even if such were to occur.