A new game client (0.0.146) is being pushed to live. Even though the update Sona square is already in this patch, another version of her new icon was picked up. [If you saw the previous news article, this is why it was re-listed as new]
This patch has no other champion changes (That can be seen from the tooltips), which means it is most likely a bug fix patch. Expect to download this patch at some point.