ZING! Yes, you did read the title correctly, I'm calling it. With the recent signing of Seahawks linebacker David Hawthorne, I believe next year we will see a defense that uses a four linebacker scheme a whole lot more and will be one of the best units in the league. Here's why...
Numbers: In just a matter of weeks, the Saints increased their linebacker total from about five to about seventeen. The injury bug was giving the Saints fits at this position last season, as it seemed none of their linebackers were completely healthy throughout the year. In fact, Jo-Lonn Dunbar, who was just recently signed by the St. Louis Rams, was the only Saints linebacker to play in every game last season. Now, that shouldn't be a problem because as of now there are 11 linebackers on the roster that will be competing for a spot.
Youth: This won't affect changing to the four linebacker scheme, but it will affect their performance. The Saints got the memo of the youth movement, and they acted fast. Their recent additions at the position Curtis Lofton (25 years old), Chamberlain (26), and Hawthorne (26) are all on the front end of their careers. The team already had players like Martez Wilson (23) and Nate Bussey (23) who will be playing in their second seasons next year. Young players at this position will help fend off that previously mentioned injury bug tremendously. If the majority of them are playing most of the games, there's a good chance for success.
Versatility: Lofton, Chamberlain, Wilson, Shanle, and Hawthorne all have experience playing multiple linebacker positions. They would be able to interchange with players like Vilma, that are more comfortable playing one specific linebacker position. This would also give Spags the ability to create more diverse packages and schemes, as not one player will be fixed to a position. One play Wilson might be inside and the next he could be blitzing off the edge from the outside position. In a 4-3 scheme that wouldn't be such a good idea because that second inside linebacker spot isn't available for leeway.
Skill: The fact that the Saints added two linebackers with the skill level of Lofton and Hawthorne in the same season(!!) is just beautiful. Both were starters on their previous teams and contributed greatly. Lofton compiled 147 total tackles while Hawthorne had a career high of 115. These two won't make a team, but they are joining decent company. Captain Jonathan Vilma was a perennial 100 tackle player before he missed a lot of time last season due to injury. Second year player Martez Wilson has tremendous upside and should be a big contributor next season. Don't forget newly acquired Chris Chamberlain and veterans Scott Shanle and Will Herring either. They might not be breakout players, but they certainly are not slouches. There is absolutely no excuse for the Saints to underperform at the linebacker position anymore.
This is just my assessment, of course, of why I think the Saints will be playing more in a four linebacker scheme next year. All of these factors just add up too perfectly and it seems like a good fit. If the Saints stay with their current three linebacker scheme then no harm, no foul. That won't affect the performance at all, as the good, skilled players will still be there. Either way, next year the Saints will have a better and obviously newer linebacking unit. I guarantee that.