A French music website, fnac.com, has a pre-order available for a new Coldplay album, without a title, but with a release date of October 24th. This is a reasonable date, but it remains unconfirmed.
The album is expected to be finished by the time of the band's next gig on 22nd July, which would mean 3 months of preparing for release, which is enough. So we now have a potential date, but I wouldn't take it as given until there is an official announcement.
Have a look at the pre-order here.