Well, the first thing that needs to happen is that all the fuck ups from Dragon Age 2 need to be fixed. The heavy reuse of areas, the waves of enemies which is not only ridiculous when they fall from the sky, but fucks up strategies and makes it hard to know when to break out your awesome, high cooldown abilities. I'm sure everyone knows by now what they DON'T want to see in it.
Anyway, what I do want to see. I would firstly like to see the world react differently to male and female PCs. As it is there is very little difference between playing one gender or another, and I think that the differences between gender and how they are treated is something that RPGs should explore. In my experience, most people react differently to someone based on their gender, and while this is reflected in how NPCs treat each other, and they do make some effort to acknowledge it for your PC, I'd like to see them go a bit further.
I would also like to see an addition of three more classes. That is, mixed classes like in Mass Effect, where you have your three pure classes (Warrior, Rogue, Mage) and then three that mix those together (Warrior/Rogue, Warrior/Mage, Rogue/Mage). I fear that none of the DA2 classes really did it for me. I played my DA2 warrior like a WR hybrid, two swords, overwhelming single target damage, but also able to take some hits and with multi target abilities. The narrower focus of DA2 was saddening to me.
Lastly, more options in dialogue. Don't just have Saint, Joker and Asshole. That's not interesting. That's not very engaging. I can't really get into such extremes, and when they are voiced going from one to another and trying to RP it makes you feel like a schizophrenic. It worked for Shepard because Shepard was a soldier with a defined way of speaking, but with Hawke you went from happy go lucky to violent thug to earnest missionary. Really, ditch the VA and ditch the limitations that implies on our choices.