WP 7.8 might get it too.
According to a yet another report from WPDang (translation), the upcoming WP8 release will allow users to take screenshots without having to download any of the third party apps.
So how do you take screens on your Windows Phone? As stated in the article, all you have to do is press the following keys:
Windows + Camera
And that’s pretty much it. After all is said and done, the data will be saved to your pictures folder for the later access.
Stay tuned.