Ah, everyone knows that the first lady you see in trailers and is confirmed LI is pretty much to be romanced by males. Only males, if we go by Bioware's history to make every 'main' lady a hetero romance.
I really hope they'll break the ice and make the main lady for women too.
Isabela doesn't count because 1) we knew she was bisexual and 2) they used different romance system.
What history?
Here is what I remember of BioWare's history and marketing:
Jade Empire was their first game with full bisexual romances and Silk Fox (bi) has more plot important than Dawn Star (the marketing focused on the different PC mostly though). ME 2 only has hetero romances as full romances. Same goes for BG2, NWN and KoTOR, unless you count the Junahi thing that flew over most player's head.
The ME games focus on default male Shepard and BioWare prefer to market human romance but even then Liara is the poster girl for ME3 (and arguably the main romance of the series).
I personally only see a trend of focusing on the male demographic, not so much on the hetero romance. And in the latest DAI trailer has 0 romance content, Cassandra is more marketed as a super important character (sort of like Duncan and we all now what happened to him).