Age has nothing to do with being able to make music! I can see Radiohead going on forever until basically one of them dies and I wouldn't mind either because they haven't made anything post-1994 that I don't appreciate.
To answer your question: Considering that they basically have 7 (8? 9? 10? I haven't been keeping track and they've done a few shows the last few weeks) new songs post The King of Limbs, of whom 5 are unrecorded (only Supercollider/The Butcher have been released on record so far) except for live performances I think they are quite close to new recording sessions. I think they're going to do that after their tour this year, so I expect a new record in 2013. Maybe 2014 who knows, it's Radiohead after all.
edit: From the new songs I especially love this one
--
http://img.imgcake.com/tyler3gifap.gif