I don't see anything wrong with
Lego coming out with new sets that might be geared more toward girls who are into more typically "girlish" things. More choices are always a good thing. And from a company standpoint, if Lego thinks that these sets will tap into a market that they've previously been unable to reach then obviously it's a good move for them to try to attract those new customers.
I am, though, really surprised that so many people don't consider most of the previous sets to be gender neutral. I definitely consider Pirates, Star Wars, Harry Potter, Ninjas, Indiana Jones, pharoahs, Cars and aliens to be equally appropriate for both girls and boys. Off the top of my head I can't think of any recent Lego sets that struck me as being intended specifically for boys, and I can't think of any I wouldn't have loved to have when I was a child. Most of my son's friends when he was smaller were girls and they enjoyed the same things he did. They'd all go to each other's houses and play with Pokemon, Playmobile, Legos, Matchbox cars and video games, and none of the girls seemed to care that nothing was pink. I have known a few girly girls who didn't like anything unless it was pink or purple and covered in sparkles and flowers and who refused to play "pretend" unless they got to be a princess, fairy or mommy, but they've been the exceptions. Most of the girls I've known enjoyed things like Star Wars, Indiana Jones and Harry Potter, and they pretended to be pirates, astronauts, adventurers and other things like that. None of those things strike me as being particularly boyish.
ETA - It does really bother me if Lego is really promoting these as being for "the other 50% of the population". I find that to be completely ridiculous and somewhat offensive. Are they trying to imply that girls shouldn't (or can't) enjoy Star Wars, Indiana Jones, space, pharoahs, robots, racecars, ninjas and Harry Potter? Or that they aren't supposed to enjoy building things with the generic Legos? Sure, there are girls who only like "girly" things but I think the vast majority of girls are much more well rounded than that. Girls have been a significant part of Lego's customer base for many years even without "girl-specific" Legos.
(Now that I've seen the sets I can say that I hate the new figures that come with them. One great thing about the previous minifigs was that they were mix and match, and almost any figure -with the exception of some aliens or droids- would work with any set and any accessories. These new things don't even look like Lego people!)