They better be adding atleast 15 new characters.
Wu: Lu Su, Cheng Pu, Han Dang, Ding Feng, Zhuge Jin
Shu: Ma Su, Ma Dai, Gao Xiang, Zhou Cang, Liao Hua
Wei: Jia Xu, Li Dian, Yu Jin, Yue Jin, Cao Hong
And for the Other characters, if they needed to add some, I'd say the Zhang Liang and Zhang Bao since if they added Zhou Cang, it'd expand on the Yellow Turban storyline. And then they could add maybe Gongsun Zan and Yuan Shu to get some of the earlier stories bigger.
As far as music is concerned, I'm hoping for some DW3/DW4 stuff. Brutal metal, but without the traditional instruments like they had in DW4(though I prefer it over DW3's soundtrack).
I want more levels, like 60 or something. Some should be huge like the YTR in DW3, some should be intricate like DW5's Nanman campaign(Shu forces), and I want them to get more interesting terrain. Like in DW3's Mt. Ding Jun how characters would go up the mountain slower and down faster, bring back things like geysers, etc. So the levels aren't based just on their size and the amount of room, but also all of the neat stuff in them.
I'm hoping for more saddles like the generic horses(I'd love to be able to start a level on them), more orbs(bring back the poison and lightning orbs!), and more items(like all of the ones from DW3, DW4, and DW5).
I'd like to see CaW like DW5, but more costumes and more customizability of the character themselves(hair, faces, body, etc) and Destiny Mode, but longer(like 20 battles or something since it'd be much better if it were longer). And, if they didn't decided to make an XL or Empires expansion, throw those modes in. Versus and Challenge modes would be very nice(though I don't play them much myself).
And overall, I think they need some improvement in gameplay. Novice should be like it is in DW5, but Chaos should be like it is in DW3(so it's actually challenging) and then the rest of the difficulties would be perportionally harder/easier. I think they could expand on their movesets how SW did. Things that could make playing atleast a little less monotonous.
All in all, if Koei would just get their heads out of their a**es and would try some innovation, bring back some favored features, and spend a bit more time on this, they could really make a great game. Something that could put DW3 to shame and have more innovation than any of it's predecesors.
Restore the Ming Dynasty in Beijing!