I suspect that the Board of Trustees for USC will give him the ultimatum of "get us to a decent bowl, or you're gone." They gave him a mulligan for his first two seasons (NY6 bowls), and he has certainly elevated the level of talent at USC (the JT Daniels to St. Brown connection will be a nightmare to defend against next year).
If he doesn't get them to something to at least a Sun Bowl, and do so with at least 9 wins, I suspect he'll be given the boot, despite assurances from the AD.
One thing for certain, he's got a full stable of talent for next year in all of the classes. These are going to mostly be "his" players, and he's been in the program for quite a while. If he can't pass the above test in 2019, then he'll most surely be gone.