Despite Indy's flirtation with an undefeated season, I don't think there is a dominant team in the NFL right now. The difference between Indy in Pittsburgh certainly wasn't that big in the AFC and I don't think the difference between Seattle and Washington is that big in the NFC.
I think Miami and Dallas are up and coming teams that just missed out on the playoffs so both conferences could see some turnover at the top. Many think highly of San Diego and KC but I'm not convinced they'll ever be more than fringe contenders but I have been wrong before.
While Seattle's OL can be dominant, I don't see the team as a whole to be dominant. I'm not trying to take anything away from the Seahawks Super Bowl season. They had a great year and are deserving NFC champs but during the regular season, they lost to Washington and beat Dallas and the Giants by only a field goal. These are the only NFC teams they played with winning records. Admittedly they were a little more impressive in the playoffs. But my point is Seattle is not that far ahead of the rest of the pack in the NFC.
And I'm not convinced that the AFC will win every year even if the Seahawks do go to the SB four years in a row. The AFC as a whole was only 4 games above .500 so it's not like the conference as a whole dominated. They were 24 games above .500 in 2004. For the last few years, with the exception of Philly, the top teams all seemed to be in the AFC. While this may still be true, I think the gap has closed here too.