There's a free dlc that makes all their uniforms and casual wear available in the mementos and palaces...lounge wear too for the protagonist. Oh And a swimsuit pack is coming i think on the 26thNo idea. I'll probably only be getting the free add-ons.
It's pretty lame that it seems like you can't get any new outfits without DLC, but it's not really a big deal. I'm digging everyone's phantom outfits anyway. I haven't seen what they all look like though, as I'm still only in the second dungeon.