The NFL slightly altered the schedule rotation a few years back in regards to both the AFCW and NFCW. The reason for that was that prior to that two teams from a division would have much shorter trips (at KC and at Denver) while two teams would have longer trips (at Oakland and at San Diego); there was a similar situation with the NFCW - at SF and Seattle as opposed to at Arizona and St. Louis.
If you look at teams from the AFC playing NFCW teams you will see that the pairings are now Arizona and San Francisco, or Seattle and St. Louis. For example this year the Ravens and Bengals were both home versus SF and Arizona and at Seattle and St. Louis; the Steelers and Browns were at SF and Arizona and home versus Seattle and St. Louis.
We already saw a one-time blip with the schedule being tweaked for the AFC West. In 2005 the Pats were home vs Oakland and San Diego and at at KC and Denver, and in 2008 it was the reverse. This year however the new format was in place, and the Pats were at Oakland and Denver, and home vs KC and San Diego. That resulted in a one-time situation where the Pats were at Oakland in 2008 and 2011, and home versus the Chiefs in both those years.
Same thing will happen with the NFCW schedule for next year. Even though Arizona was at New England in 2008 they'll play in Foxboro again in 2012, and the Pats will be in Seattle again even though they were there in 2008.
The bottom line is that in 2012 the Pats are at home versus San Francisco, Arizona, and the first place team from the AFC West; they'll be on the road at Seattle, St. Louis, and the first place team from the AFC North.
For those questioning why the Pats are at Pittsburgh two years in a row, that too is just part of the NFL schedule rotation. We play the AFCN team that finishes in the same place as the Pats did in their house two years in a row, then they play in Foxboro two years in a row. We constantly saw the same thing happen playing the Colts, where it would be three years here then three years then when you also factor in the AFCE versus the AFCS.