I say no, for the following reasons...

First, the 3-4 has worked well so far and the system is in place and the players know it.

Second, we have good talent at LB, no need to fix what isn't broken.

Lastly, we are actually beginning to increase depth along the DL, making the 3-4 all the more viable.

Coaches Kaufusi and Tidwell will have (barring injury) alot of bodies to rotate in at both LB and DL, keeping the athletes fresh to close out games in the 4th quarter. With returning guys like Jorgensen, Tialavea (fingers crossed) and the addition of Tevita Hola and other recruits, the DL should be strong. Besides, BYU can unofficially line up in a psuedo 4-3 anytime they want by inserting a larger LB and moving him up to the line of scrimmage for certain situations.

Part of the reason that an undersized Jan Jorgenson can create havoc in the backfield is the need for linemen to pick up backers coming in.

The 4-3 is a no brainer scheme for when you have a Percy Snow, Andy Katzenmoyer (Ray Lewis) type of MLB that gobbles up everything in front of them and has it funneled to them by big beefy Dlinemen. (i.e. Shay Miurbrook,Rob Morris, -Rob Morris had 114 unassisted tackles in 1998-the NCAA record is 135-) and huge D linemen that can force the offensive line certain directions. There was a time when it was a pretty viable defense for us.
Although, when you shut down 4 of our JUCO feeder schools and all of a sudden, we don't have an overflowing supply of Jason Bucks, Shawn Nuas, etc.
Literally Dline was a major strength in the 80s and 90s and even a bit beyond (that 01 team placed Denney, Hoke, Keisel, Nua etc. in the NFL). Even when we lost games we had a good Dline.

http://www.ncaa.org/library/records/football/football_records_book/2007/2007_d1_football_records_book.pdf

The 3-4 is less of a matter of size and talent (although it certainly helps) and more heart and execution. Be in the right place at the right time, and make tackles when you have to.

Our current Dline players are good, but I guarantee half wouldn't start at many other D1 schools, primarily because they're not suited to a 4-3.

You have to credit Bronco for caring more about winning than his own system. When it was obvious that his system wasn't working, he adapted. That is one of the more glaring differences between he and Gary C.

The 3-4 suits a program that can recruit the heck out of small linemen and big safeties that are smart and can tackle-and fill the roster with guys that can also play special teams. (This is tougher to do when you have 16 6'5" 280 dlinemen on the roster).

I see the 3-4 as becoming more the mainstream defense. There are a lot of teams that play 4-3 but I think that goes back to the 3 yards and a cloud of dust offensive philosophy. When most teams ran the ball 80% of the time it made sense to have big beefy guys up front. With the advent of the West Coast offense, option, run n' shoot, spread, spread option, etc teams are finding in more useful to have more speed and flexibility on defense which the 3-4 provides. A lot of teams still play very good defense with a 4-3 but I think the trend is shifting.

If it ain't broke, Don't fix it...

If you look at the toughest and most notorious NFL defenses over the past few decades you have to look at the Pittsburgh Steelers and they use the 3-4. Guys like Porter and Foote were big to their defense.

NO!