Right now it is about 66%. If Chiefs win tonight, it goes up to roughly 85%. That is very far from lock in my book, though obviously very likely.
Even if Chiefs win tonight, if in W17 Titans beat Texans and Chargers beat Chiefs (which is not impossible) then we play Chiefs.
And if Chiefs somehow lose tonight, it shifts to 66% that we actually play Chiefs. Like Cajun sadi above, at least wait for Chiefs game before you make arrangements.