If the Colts win against the Titans next week, they are in the playoffs. They will also win the AFC South division and host a playoff game. What the Jaguars do Sunday against the Texans won't matter. Colts win, and they are in.
If the Jaguars win Sunday and the Colts lose, the Jags would go to the playoffs due to a better division record.
If the Colts lose and the Jaguars lose, the Colts win the South due to having a better overall record. The Colts (9-6) currently have a one-game advantage over the Jaguars (8-7).
It is still possible for the Colts to have the #3 seed if they win the AFC South. If the Chiefs lose against the Raiders next week, and the Colts win, both KC and Indy would have 10-6 records. Indy wins the tiebreaker because they defeated KC earlier in the season.
Both the Colts and Jaguars games were moved to 4pm Eastern on Sunday. Make no mistake, that move was to make the Colts play starters. The NFL does not want a repeat of last season.