I am not sure if Johnson would see much more targets in NE than with the Texans. Think about it we already have Gronk, Edelman and LaFell sharing the most of the targets. I doubt he wants to play mostly decoy which is what I guess the plan for him in Houston was.
Looking at the Packers and - to a lesser degree - the Colts they have a similar situation where he would be sharing a lot of targets with other weapons.
I seriously think that the Seahawks might be the most attractive option if he really wants to be a main target in an offense.