Aldo is such a terrible match up for Frankie. I don't think this is a good move for him in the long run. Benson Henderson isn't the guy to hold the LW belt for years to come, I don't see him getting by Nate Diaz.
He has a decent speed advantage at LW, but let's see how that converts once he drops down to a lighter weight class.
He has major trouble with kickers and Jose Aldo is an elite, hell, perhaps one of the best low kickers in MMA today.
He's faster than Edgar, a better striker and has some really slick TDD.
If he even gets a shot at Aldo (Zombie ftw), I can see Jose murdering him.