Duplo sets are fairly unisex, as has been mentioned by TLG as getting about the same attention from boys and girls. But after that age range, girls and boys begin trying actively to differentiate themselves from one another. TLG has a hard enough time competing with other toy companies as it is-- if they were to just hope for girls and boys to buy the same things, then they'd basically be setting themselves up against peer pressure and every other cultural influence that feeds this arbitrary differentiation of gendered play. That's not a healthy competitive situation.
And as I mentioned about City sets, the current range of LEGO products tends to include things like vehicles and conflict role-play that for whatever reason boys tend to flock towards and girls tend to ignore. Yes, it's true that girls and boys should be able to enjoy the same things, but as it is they don't, and I think it's wise of TLG to try balancing out their offerings to appeal to girls of diverse interests rather than just telling the girls who want to play with toys considered "girly" that they are the product of a hypocritical society, that their interests are stereotypical and demeaning, and that they should outright reject their friends who think Barbie dolls and Littlest Pet Shop are the coolest things on store shelves.
Or, they could try to get girls and boys to play together and have a mutual respect during the "cooties" stage. In that case, my only suggestion to them would be that they might have better luck with their plans to use their toy-company influence to end world hunger, childhood obesity, and natural disasters, all while turning a significant profit from the endeavor.
On a side note, when I was in elementary school, one of the biggest recess activities was for all the boys to chase after all the girls and the girls to run frantically. I thought it was a stupid, biased activity, and when I did participate I would try to team up with the girls (don't draw any sexual conclusions, please). Was I popular with both genders? Well, they did treat me fairly equally... as a social outcast and a weirdo. You're basically saying TLG should likewise try to fight against this alarming gender divide in preteens, so naturally I'm a bit cynical about this approach. I mean no insult towards girls, towards women, or towards those like yourself who honestly want to work towards gender equality in society, but I merely lack confidence in the strategy you feel TLG should take.