Yeah, I would make the conclusion that is would be really difficult to do such a thing. Mentally, we compartmentalize everything. We have different types of memories, different areas for different processing, different schemas for different subjects, etc. It would ultimately be very difficult to be able to think of "he" and "she" as the same "they", mostly due to our society and how we work, in social terms. However, in the right environment, one where man and woman has not been organized as two separate things - basically, a world without any idea for "gender" - it would be possible. It can also be possible with deliberate retraining, with purposeful "reorganizing" of your schemas within gender, but that's hard to do when all around us men are masculine.and women and feminine.
If you're talking about bias and generalization because of gender (gender roles and all that), then it is still difficult to see things as wholly equal, but it would be a lot more possible. The reason it is so difficult would be attributed to our society again; its just how we roll. The original classifications and assignments for each gender weren't made willy-nilly, however. Most were made for perfectly fine reasons. For instance, men are just biologically primed to be stronger and larger than women, in terms of mass and muscle, so it wasn't a big leap to classify men as the more "tough" and "protective guardian" gender, when it is easier for them to be the protector, due to their body composition. Women can make babies, men can't. Thus, women began stereotyped as the "homemakers" and all that. It was just a natural order of events, a normal train of thought.
Now, that's not to say gender roles can't switch around and change because they can. It's just that the ones we have now were not made for no good reason. It should also be noteworthy that our society, as it currently is, is a lot more "equal" between the genders than we have been in the last few hundred years, so there's that at least.