Of course we need to let the offense adjust to the loss of a coordinator, but i disgree that it's guaranteed to get better.
An offensive coordinator is more a specialist, an artist, if you will. You can plan all year and all week for what you'd like to do, but making it work, putting the defense off balance, is another thing.
Then of course, there's the situation where the defense has a book on you and is determined to stop what you plan to do.
You either have a feel for adjustments, or for setting up the defense for future play calls in crunch time, or you don't.
Designing a ton of pass plays, then marveling at the talents of Moss, Welker and Brady, does not necessarily constitute creative play calling. Everyone's a genius in 50 point wins.
Weis is an offensive coordinator, that's why 6 teams are supposedly after him. McDaniels is a smart and driven guy. I'm not convinced he used the outlandish talents in 2007 to take advantage of the defense to kill teams with easy scores when they overplayed. Everyone looks at the SB as if it was a fluke, but our offense peaked in week 11 and we never took what defenses gave us, leaving us one dimensional and more easily defensed.
Play designing makes for awesome high scoring games. Play calling means keeping the defense off balance and having a couple can't miss plays you set up, available for crunch time.