My 2 cents on Fujin...
I think Fujin is a big mystery and can go either way. Personally, I think they don't have any big plans for him and he was in MKX mainly because he had to. I think they know there is fan demand for him, but at the same time I think they don't know what to do with him because of Raiden. They could revamp him a bit in terms of how he looks and slightly gameplay-wise, but I think his integration into the story is what's causing the delay. It will all depend on what they do with Raiden in MK11. If Raiden dies (who cares he's a god) or he realizes he screwed up and steps down, I could see Fujin being finally in and taking his place. If Raiden doesn't die and actually becomes a hero, then I don't know. He could join the Elder God club and just become a face in the sky, thus giving room Fujin, or he could be as he is (dark or normal) and continue doing his thing - lowering Fujin's odds. The other way I see Fujin being in is if Raiden seeks his help in MK11, because he's overpowered. But I'm not sure that will happen. This depends on who's going to be the villain. If Shang Tsung is returning, which is hinted at, maybe Dark Raiden could take him out by himself. But then there's also Kitana and Liu Kang. Will they join Shang Tsung and create the new "deadly alliance"? These 3 could be a lot to handle even for Raiden, imo. Not to mention Havik will possibly be lurking around the corner. Can Raiden take down Shang Tsung, probably more powerful than before, Liu Kang, Kitana and Havik all on his own? Nah, doubt it. So... Who's he gonna call? Ghostbusters! LMAO, seriously, though. Fujin would be his best bet. Johnny is out, Sonya is out, Jax is out, Kenshi is out. If they're in MK11, they're going to be only cameos giving advice and support. That leaves the new guys - Cassie, Kung Jin, Takeda and Jacqui. These four? They'll have to be there, we know, but I don't see them playing a major role this time. They will help, for sure, but heroes? No. Just no. So... Who else? Then there's only Li Mei, Bo Rai Cho and Sareena. These 3 I can see getting a larger role and being playable. Shujinko? Taven? Could be, but those really are a big mystery as well. Hard to guess if/how they'll include them. I'm not ruling it out, but then again... It would be imo a bit lame if Taven was the hero. Plus I doubt they're going to just copy the events. So realistically Raiden will have, if he'll feel like it, only 9 characters to ask for help. 9 + Fujin. Fujin imo is more powerful than most of those 9 characters and would be useful. I think they're simply holding him back to give him more room in MK11. Because adding him to MKX would have almost zero value due to how small his role was and because it seems they don't think he would fit. If they really wanted him playable, he would be. But he didn't make it as MK9 DLC, MKX main nor MKX DLC - despite there being some plans. I think that says a lot. I think if he's one of the additional characters for MKX, it will really be purely because of fan demand and they'll ignore him in MK11. Personally, I'd rather see him in MK11 than in MKX. Give him the room he deserves.
As for who deserves to be DLC the most, apart from Fujin? Sareena. Why? Because of her ties to Shinnok and Quan-Chi and MKX's story. With both of them being killed off, I'm not sure what they could do with her story-wise in MK11. Now's the time to bring her back and revamp her. She could have something interesting to say to Sub-Zero, Scorpion or Tanya as well. And after her? Baraka.