This is purely speculation, but I would suspect that there are only going to be 4 LI's in DA: I. I'm basing this off of a statement that I remember (and of course that I don't have the source for.....) where one of the devs said that they weren't expanding the resources for romances. So since DA has always had 4 LI's, I'm assuming that DA: I will too.
Since Gaider has stated numerous times that, while he'd prefer to have a variety of sexual orientations among the LI's, he would always choose to have equal distribution of LI's for PCs of every orientation versus multiple choices for some PCs and no choice for others (such as the terribly unequal DA: O dynamic). So based on this, I'm also going to assume that this means that the LIs will all be bisexual again.
If I had to choose from what we know so far (which is really limited), I would suspect that LIs will be Vivienne and "Sera" (i.e. blonde elf lady) for the ladies. I think "Sera" would fill the playful LI role, plus she's a rogue and we've always had a rogue female LI. I go back and forth on Cass versus Vivienne and I lean to Vivienne because I could easily see Cass playing the Aveline role in being a serious goal oriented companion who isn't interested in romance with their friend. Vivienne would offer a nice variety as she represents a culture (flamboyant Orlais) that we know little about so far. Although the fact that Gaider is writing multiple romances throws a wrench in this plan. It could just as easily be "Sera" and Cass.
For the guys, I would suspect Bald Elf Guy ("Baldy") as one since they always have an elf guy romance and he's being written by Gaider (right?). The other one is too hard to tell. I suspect that Varric will not be, to continue his role as the "bro" and, although I hope I'm wrong, I don't seem them including Bearded Grey Warden, since he goes against the "boy next door" type that Bioware often uses for the male LI's. He's older, bearded, and muscley. While that sounds awesome to me (and several others, based on past coments), I think he's out. That means that it would be one of the remaining unconfirmed guys. Of course, my vote is Cullen, if he is in since he fits the stereotype much more closely, but that's to be seen, I guess.