TEASER: "Downton Abbey" Season 5

A new 20 second teaser for the fifth season of Downton Abbey has been released. The drama is set to come back in the fall on ITV in the UK, while the US has to wait until January every year for the PBS run. I'm wondering just how long Downton can keep going at this point, seeing how Julian Fellowes writes every episode himself. Can the house last into the 1930's?