More on her visit:
http://www.people.com/people/package/gallery/0,,20395222_20907646,00.html
http://greatideas.people.com/2015/03/13/kate-middleton-downton-abbey-mrs-patmore/
So it’s official. The next season will be the last.
I think it makes sense. It seems they’re laying the groundwork to pair people off or set them on a new path, leaving Robert and Cora to say good bye.
I was hoping to see how Robert, Mary and the rest cope with the 1929 stock market crash. But I doubt this last season will move that far forward. (Unless we get an Animal House-style ending showing us everyone’s ultimate fate.)
Final season: Downton abbey is crossed with that great movie Clue and everyone is framed for murder and goes to prison- except of course Barrow who actually is the serial killer. 
Ooh, it would be great if both Anna and Mr. Bates are exonerated in the case of Mr. Green, and then we find out they are a serial killing couple. The last episode–directed by [del]Quentin Tarantino[/del] Robert Rodriguez–is the two of them just murdering everybody else in the house using shoe horns and soup ladles and silver-handled combs. And maybe shotguns.