According to a blurb on Kotaku, a teaser for the game is supposed to be released tomorrow. While only a single screenshot has been submitted so far by 3D Realms, according to George Broussard of 3D Realms a video trailer has been made that will be released tomorrow.
I'm extremely skeptical, as should anyone who has been reading up on 3D Realms the past few years. Tomorrow we'll know for sure, though it is definitely exciting to think this game might actually be a reality. Then again, sometimes rumors are just rumors.