This is true. However we are talking about actresses that are that age now...but will be old enough in 3-5 years when the movie gets the green-light and casting starts.
I like Emily Blunt and think she is a good actresses...but in all honesty I don't think she has the amazonian look that would be right for WW. I think Gemma Arterton has a better look for WW than Blunt, but I still wouldn't necessarily want to see her in the role either. Now of course I wouln't condemn the movie if either actresses were in it, but just saying they wouldn't be in my top 5, let alone 10 (maybe).
I'm glad a lot of people are looking for top notch actresses, but keep in mind this movie will probably be along the lines of Avengers, LOTR, the Hobbit. There were fine performances from all actors in those films, and many of those actors were not household names or even cult names before being cast in those films. Not saying all, just saying many.
I personally would want a decent/good/great actor over a big name that looks the part rather than a big name decent/good/great actor that doesn't look the part.