New Coldplay album coming this December?

Nice guy stadium rockers Coldplay appear to have stealthily announced when their next album will drop.
A poster displayed in the London Underground bearing the date "December 4" and a symbol that looks remarkably like the one Chris Martin had plastered on his t-shirt at the Global Citizen Festival (as well as mirroring the imagery on their online "Timeline") would seem to suggest they've just made a quiet announcement to the world.
This eagle-eyed passerby joined the dots on Twitter last night:

Anyone else spotted this mystery London Underground poster tonight? Yep, it's the new Coldplay album. December 4th. pic.twitter.com/Jk0ArzMhJu

— Lee Thompson (@leethommo) October 29, 2015

Adds up to us...

A photo posted by Atlas Project (@atlasproject) on Oct 29, 2015 at 4:35pm PDT

Set to be called A Head Full Of Dreams, it will follow hot on the heels form last year's Ghost Stories and will be their seventh album to date.
Chris Martin has recently said of the new work:
It's our seventh thing, and the way we look at it, it's like the last Harry Potter book or something like that. Not to say that there might not be another thing one day, but this is the completion of something… I have to think of it as the final thing we're doing. Otherwise we wouldn't put everything into it."