There’s no other object in the photo for comparison to show how big the screen cover really is, so you can’t really tell if it is larger or not.
The image was leaked by iDealsChina. According to source:
“China's 1st iPhone 5 photo has surfaced! From this photo it seems that the screen size will be larger than iPhone 4. There has been a lot of specualtion about a larger screen and maybe this will be one of the upgrades we will see when iPhone 5 is released this summer.”
The iPhone 5 is still months away from any announcement, so expect a lot more speculations until then.