Of course one other interesting scenario: Patriots beat Pitt while all 3 teams (Jags, Pitt, Patriots) win all their remaining games:
Patriots #1
Jags #2
Steelers #3
KC#4 (assuming KC doesn't tank so bad the Chargers overtake them)
Assuming Pitt wins their WC round game against the Ravens (I'm guessing it is the Ravens and I'd assume Pitt will beat them), AFCD Weekend:
Steelers @ Jags
______ @ Patriots (IMHO likely KC but given how bad KC is now playing there is a fair but outside shot at it being the Titans)
That's a pretty sweet AFCD matchup for the Patriots either way -- while the Jags and Steelers beat the defensive crap out of each other before one of them has to come to Foxboro (a Pitt team that has been pretty bad against the Patriots in Foxboro or a warmer weather team Jags with little PO experience and questionable offensive prowess).
That's a pretty optimal scenario if it plays out that way (though 3 teams going 6-0, 6-0, 5-1 in their last 6 seems wildly unlikely).