Baraka will absolutely be in the game. He is so scary and popular! There is no other character like him. I'm sure they will probably reproduce his impale and lift fatality to some degree. I hope this time they make him due it slower and creepier!
Also, Jade was a huge enigmatic entity in MK2. They wouldn't dare make this game without her.
I loved playing as Rain in MKT. Was Rain playable in the wide arcade release of UMK3? I've heard there was a late revision where he made an appearance, but I'm referring to the version everybody actually played. I do know he was available in the SNES release of UMK3 If NRS is basing their idea of UMK3 on the arcade version, Rain's chances might be slim, since there are so many ninjas already. This isn't ninja kombat. If they bring him back, and I hope they do, he needs a model overhaul! They did a great job with Ermac, and I have faith they can do it for Rain.