Entering the 2010 offseason, there were a lot of Patriots fans that felt that the team was transitioning to a 4-3, and away from the 3-4 that they had used for most of the last decade.
After all, the Patriots had played the 4-3 for the beginning portion of 2009, and seemed to have a lot of personnel that could switch between both schemes (Jerod Mayo, Gary Guyton, Vince Wilfork, Myron Pryor, Ty Warren, etc.) Even when the Patriots re-signed Vince Wilfork, they still had the possibility to move to a 4-3. And I think a lot of fans even anticipated a full time switch.
Of course, the Patriots' 4-3 from last season was a little bit different than your typical 4-3. It was more of a 2-gap defense, often with an outside linebacker lining up over the tackle/tight end and blitzing the quarterback (in some ways, this was similar to the 3-4).
While the Patriots will still likely mix up schemes a little, I am personally a fan of the 3-4, and looking over the Patriots' selections, I believe they made a firm commitment to that scheme. I think this was an often overlooked subject in all of the post-draft analysis.
A look at some of the Patriots' selections, and how they fit the 3-4:
Jermaine Cunningham: While Cunningham could be a 4-3 end, he was drafted as an outside linebacker, and looks like he will be best suited on his feet in the pros. This pick certainly reflects the Patriots' commitment to the 3-4, as Cunningham fits the bill as your typical Patriots' 3-4 outside linebacker.
Brandon Spikes: Spikes probably lacks the range to be an every down 4-3 middle linebacker. However, he should be a great fit as a 3-4 inside linebacker, as he will likely eventually start next to Jerod Mayo at strong inside linebacker.
Brandon Deaderick and Kade Weston: Both of these guys are 3-4 ends. If the Patriots were switching to a 4-3, they wouldn't need any more 4-3 defensive tackles, with Vince Wilfork, Ron Brace, Ty Warren, Myron Pryor, Darryl Richard, Mike Wright, Gerard Warren, Damione Lewis, and Adrian Grady. I think both of these picks were taken with the idea that they will be 3-4 ends (heck, Deaderick played that position at Alabama) in the Patriots' scheme, hence showing a firm commitment to the 3-4.
I would like to note that I do not believe the Patriots will completely abandon the 4-3. The ability to change schemes at a moment's notice is part of what makes Bill Belichick's defenses dangerous and unpredictable. However, upon closer inspection, it looks like the Patriots' 2010 draft picks reflect that the Patriots will be sticking to the 3-4 for the foreseeable future.