The following was posted on Green Day's official Facebook page last night
"This Monday, a new song from ¡Dos! will premiere in Idiot Club! Make sure you're a member if you aren't already!/"
You can register for the Idiot Club here. If you pre-ordered the Ultimate Box Set from GreenDay.com, it came with an Idiot Club account which you should have received an email with directions to activate your account.
Here's the full track list for ¡Dos!, what song do you hope we get?