Well, from the statements we got last spring it would appear that rather than "rewriting" the existing romance arcs they're going to write entirely new ones. Because they had the idea that switching pronouns is lazy and unprofessional, despite that being more or less what's done in those other two BioWare franchises.
But, again, the writing shouldn't be the problem. The biggest hurdle should be paying all those voice actors to come back. That needs to happen even if they're just switching out some pronouns and most of the new dialogue is done with the core 16 voice actors. (Keep that in mind: to get one SGRA per class and gender, they'd need to work with a minimum of 32 voice actors.)
Past Bioware games do not simply switch pronouns. Usually you have different dialog/cutscenes matching the gender of the player.
If this thread
is true, even the straight romances are coded rather poorly with no way to exit a once started romance arc. So it all romances are in dire need of rework.
I donīt think that the voice acting is that much of an issue. Since there is plenty of other dialog that needs to be recorded too so it would not be like bringing a voice actor back just for 15 minutes of dialog.