The defense isn't that old. They have youth at LB and DL and Both Bly and Bailey should still be productive. I see no reason to panic. Denver just needs all of the drafts to pan out. 2006 looks dynamite. If the 2007, 2008 and 2009 drafts turn out good than Denver will be sitting in a good position in 2010.
I do believe Denver has to be careful on how they resign their players with the 2010 season looming. I think the NFL and the players union will come to an agreement before that. From what I have been hearing the uncapped year really isn't going to be that good of a thing for players and that a lot of older players will lose their jobs in an uncapped year.