Fox has college football. If Biden speaks at 8, the kickoff can be delayed. If not, they can tell people to watch Fox News.
CBS' only first run is the live eviction episode of "Big Brother" at 9. If Biden speaks at 9, they can just tell the guinea pigs that the show will be delayed an hour.
NBC is all-repeat "L&O" Thursday.
ABC is all first run, but will probably pre-empt one of the game shows and run a repeat of the other. Since "The Con" is the weak link in the lineup, they may just run the new episode.