I think some are forgetting what Shanahan was building in Denver on offense before he was fired and then the whole thing was dismantled by the idiocy of McDaniel.
Shanahan's fault was defense, as was covered heavily in a thread in ES not too long ago. He found a good DC in Denver but let him go for some reason, this time around he seems to have had more patience by letting Haslett stay. However, I think I saw the insiders say that Morris has had a bigger hand in things lately. If true, then Morris replacing Haslett next season could mean a good defense, in which case the team becomes one of the top ones.
My concerns are not with offense, but with defense. I am confident Shanny can maintain a great offense. All we need is a decent DC.
I also think the NE "dynasty" stuff is overblown. To have a team that annually is in the playoffs and a contender is ideal. To expect 3 superbowl wins over 4 years in this league is an unrealistic expectation IMO and an attitude that could lead one to repeating Snyder's old habit of firing coaches too soon. NE, afterall, was incredibly lucky to even get to the superbowl in 2001, with the tuck rule, the forward lateral vs. Pitt, and then Warner having a broken thumb. Then there is also the unknown of how much the illegal taping helped.