Since we're dealing in hypotheticals...

Woodley would be a DE if the Steelers ever changed to a 4-3...but, he would most likely be an "elephant" type DE...also known in some defenses as a "Leo" or even a "Jack"...that type of DE plays as a standup player who basically plays DE like an 3-4 OLB...

Really, the only differences between LeBeau's 3-4 and most 4-3 Ds are gap responsibility...the players on LeBeau's 3 man line are all 2 gap defenders...most 4-3 D-Linemen are one gap defenders (with the exception of the 4-3 NT, for the most part)...

If you lined up the defense in a 4 man line, with a "Leo" DE, the front would be virtually indistinguishable from a 3-4 front...the difference would be gap responsibilities...

Short story long, the Steelers are most likely going to be spending less and less time in the base defense and more time in special packages, so the base D becomes increasingly irrelevant...