I got a few predictions on the replacement game. I think it'll be one of these.
Lions @ Saints
Bengals @ Steelers
Broncos @ Vikings
Packers @ Giants
Falcons @ Texans (The least possible prediction)
I'm pretty sure that you can rule out Packers-Giants. Both Fox and CBS can protect five games each between Weeks 10 and 15 (week 16 is Xmas Night and Bears-Packers is locked in there, and week 17 the entire schedule is subject to the flex), I saw the list earlier this year, and I'm pretty sure GB-NYG was one of the games Fox protected.
I think the game to be flexed in will be Lions-Saints, with Falcons-Texans and Bengals-Steelers also in the running. I think you can all but rule out Broncos-Vikings.