Does anyone know ?

Some people did some calculations and guessed double the size of Skyrim,but they can't be sure,especially because the don't know where the map ends. Otherwise nope,only fake leaks.

yup. heres the research right here.

http://imgur.com/gallery/lFIxR/new?forcedesktop=1

Larger than Skyrim would be awesome. I love to explore.

This does not tell you anything. It is still all guess work and there is no way to know how real life Boston has been scaled down in game to fit in the various landmarks shown

The game could still be anywhere from same size as Skyrim to 3x larger

your right. its just a theory. its not official. but still they did research on their own and thats whats been concluded

I kind of doubt it's muth larger, it's possible but still, The impression I got a while Bach was they thought Skyrim was more or less the perfect size.

I also hope that the density would be much smaller, it's a wasteland after all.

Maybe with some little towns/fortress here and there, you know?