Rain is likely be DLC since he has a lot of request to be DLC. Boon said on Twitter that we might see free DLC, I'm pretty sure the classic outfits (For Sub Zero, Reptile, Scorpion, Smoke, Noob, and Jade) will be free since they where on the disc. Don't charge us like $5 or $10 for them.
I would like to see Quan Chi's MK4 outfit to be DLC as well.