If Cincinnati beats Denver on Monday Night Football, the Bengals will have clinched a first-round bye (they already have won the AFC North with the Steelers' loss to the Ravens).
The win will not get Cincinnati out of the No. 2 seed at this point though. New England will retain it despite both being 12-3 as the Patriots have the common-opponents advantage over the Bengals (4-1 to 3-2).
A Bengals win would also clinch the AFC South title for Houston. That would clinch a strenth of victory tiebreaker advantage for Houston over Indianapolis, and would also eliminate Indy. That win would also bump Denver behind Kansas City in the AFC West, which would move the Broncos to a No. 6 seed through Week 16, with the Chiefs controlling their own playoff fate for the AFC West crown.
If Denver can win on Monday night, the Broncos would lock up a playoff spot and would be the No. 2 seed with control to win that seed.