This could be the final year of truly dominant defense. Not to say the defense won't survive the losses of Wright, Smith, Avril, Maxwell, etc., only that this year's defense has a CHANCE to be one of the greatest of all time, surpassing the defense of last season.
The pass rushing combination of Avril, Bennett, and Irvin has a chance to be truly great; that's something we only saw in bursts last year because Bennett/Avril were adjusting to playing together and in this defense for the first time, and Irvin was used too much at SLB rather than rushing the passer at LEO or the five technique.
The depth at LB is pretty extraordinary right now. Wright, Wagner, Smith, plus Irvin as a rotational player, forms a pretty formidable combination. The LB corps could look completely different after this year, and there will undoubtedly be an adjustment period. if they lose Wright, Irvin will be needed again as the full-time SLB, rather than having more opportunities to rush the passer.
And the secondary is full of guys playing in their prime. Having both Maxwell and Lane at CB is huge. Maxwell is a free agent after this year, and Lane is a free agent after the next year. The amount of talent they have stockpiled over the last four years is amazing, but it will be hard to maintain now that these rookie contracts are being converted into massive, cap-eating deals.