This is why I use multiple game saves that are named differently, according to their content and mods used. I started that practice for testing things after patch updates. I have 2 or 3 saves with no custom content or mods, a save with only career mods, a save with only trait mods, several legacy saves with all mods and cc used, and several saves with only custom content. Neia's career tool is confirmed that it will be updated after the November patch, and she expects most things to be able to work, with adjustments. Individual custom careers will have to be updated as well. MCCC is also confirmed that it will be updated for the November patch. However, I expect to probably wait a week or two after the actual patch before the career mods and MCCC will work.
Unfortunately, I still don't know if the food mods and trait mods I have in my game will be updated or not, hopefully they will be. And I probably won't be able to play my Go To School save (which uses Zerbu's go to school mod) again the same way. Lifestate mods, like genie mod or mermaid mod or robots mod will also probably not work anymore, so I may not be able to play saves with those mods, unless I want some of my Sims to lose the associated traits, or have the associated objects broken (and without a charging station...the robots trait would not be a good thing).
I plan to play with the mods I have until November, then in November start playing only with my custom content saves. Custom content will be automatically disabled the first time the game runs after the patch. Then, before I enable any script mods, I plan to remove all existing script mods, and replace them with updated versions that come out after the patch.