A video on the Destiny YouTube Channel simply states 'coming soon' in its title and within the video itself, with a short glimpse at three guardians striking a pose.
Initially I thought this wasn't hinting at anything, as the video is actually embedded within the new Destiny Planet View feature - the video appears when you click on certain icons in the feature to find out more about the area you're in, which made me think they would just be adding that informative content at a later date. Plus, the video isn't listed on the YouTube channel, it's only accesible via the link. However, the video was actually shared on Destiny's social media sites like Facebook and Google+ stating 'Tomorrow: something is coming. Stay vigilant, Guardians.'
So, what could this announcement be? New content? We'll have to keep an eye out today and see.