OK, when we say 'teaser' we really mean it's a 'teeeeaaaaaaayser'. It's nary a 20 second voice over from 'Carson' (Jim Carter) rumbling a rumination about the future of Downton being in a state of flux.
According to Digital Spy, new cast member additions include Sue Johnston (Gloria off Corrie and Baaahbarah off The Royle Family), Anna Chancellor (Questular Rontok from The Hitchhiker's Guide to the Galaxy), and Richard E Grant (forever Withnail).
Season 5 of Downton is due to air on ITV in the autumn. No exact air date has been released as yet.