I don't know. After 69 years, why change it? Considering the backstory around the costume from my understanding, I find it a bit strange for Wonder Woman to change it. Outside of the top, the rest of the outfit doesn't give me a superhero vibe.
Don't worry. They'll change it back in a couple of years at the most. It's just more lameass posturing to try to draw in new fans.
It's sad, but superhero comics are dying again (much like the early 90s). They keep doing stuff like this to try to revive interest, but it never works.