Offenses in the Big12 and college football in general are becoming more and more wide open, utilizing small, faster players in 'tweener' roles as well as a wide variety of blocking schemes, splits, formations, no-huddles etc.  

Has the 4-3 defense become outdated?

Unless you have the right players, I think it has.  Defenses today have to be able to adjust to a variety of looks with the same personnel -- especially in conferences where so many teams utilizing the no-huddle.

Mack has dones a pretty good job in getting ahead of rule changes and trends.  But given the amount of spread teams that we play next year (and teams that have been very successful at it at that), I think we need to add wrinkles to a 4-3 defense to adjust.

A good starting point would be the missouri/kansas game.  Mizzou's defense utilized a ton of blitzing from the weakside and dropped very athletic ends and linebackers into coverage.  In many ways the versatility of the ends and LBs reminded me of New England.  This to me, is the blueprint.

The potential is there for guys like Houston, Kindle, and Dravanti Johnson to play "inbetween" roles.  All of these guys have the size, strength, and speed to line-up on the edge and rush or to drop back into coverage.  That's basically what a 3-4 is anyways.  It's all about personnel and match-ups, and Mack needs to find ways to tilt these back into our favor.