With the Pats, they'll be a Championship contender every year until Brady retires, then they'll have to take a step back; my expectation would be to a team like what we saw last year, not all the way back to "total rebuild." That's why you have to keep retooling, let guys who might still help go if they're keeping the younger guys from getting better and taking over.
My opinion; the best that any franchise can realistically hope to achieve is probably what the Pittsburg Steelers have done. It's not that they won the title last year; how often has Pittsburg *not* been among the better teams in the league over the past two decades? In the seventeen years since Chuck Noll retired, they've only missed the playoffs five times (three of those from '98 to '-00, when they were still a combined 22-26). Two Championships and anther SB appearance. That's a helluva accomlishment, a helluva lot of good players who have come and gone (and not a lot of high draft picks to help).
I think that's the model that the Pats would love to emulate; be consistently in a position where, if a few things break your way, you get lucky with a few draft picks, you can make some noise and be competitive each and every year. I mean, we've seen in recent years how teams that were relatively medicore in the regular season caught fire at the end of the season and won the championship (the G-Men) or just came real [dang] close (the Cards last year). Put yourself in a position every year so that when you DO get a little luck, you can take advantage of it.