The Saints' signing of Curtis Lofton is significant for a number of reasons. His numbers over the last four years have been solid. 100+ tackles per year, and although he's not that every-down linebacker that Vilma is, he's a real run-stuffer, and can flat-out hit out.
He's a four-year veteran out of Oklahoma, and for those Who Dats wearing a #51 jersey, I think the writing is on the wall.
Vilma is five years older than Lofton, both are middle linebackers, and I don't see a scenario where you'd move either one of them to the outside. I think common sense says they don't have Vilma in their plans, but you never know.
Also, this is a good sign of things still clicking on Airline Drive. Even with the "bounty gate" black eye, this front office is still making New Orleans an attractive landing spot for free agents. You can clearly see that Mickey Loomis is intent on improving the football team, despite all the distractions of the scandal.