Jason Taylor wouldnt be a reason why we wouldnt switch to the 3-4, he would be a reason WHY we would. He's got the speed to cover, the size and strength to shed blocks, and he'd be lined up at a wider angle, helping use his speed, which would be above average for 3-4 pass rushing OLBs, much less DEs.
The problem is, the other players. You need big linebackers for a 3-4. Look at the Steelers or Patriots. Your linebackers need to be able to take on a linemen some of the time and still be effective. Zach Thomas, Eddie Moore, Morlon Greenwood, Tony Bua, Derrick Pope..Those are all entirely too small. The only linebackers who ISNT, and is big and strong enough to shed tackles consistantly is Seau.