I have a copy from 2009 (taken from a 5D2Kit) that I selected at my local Frankfurt/M. dealer and I am quite happy with it on the 40D and 7D and I also think that Canon will update other lenses but not his one.
Of course a new design inherited from 70-200 2.8 L Mk II and the latest Mk II of the 24-70 would be nice...
but
let's hope they announce one next year so we probably see (and talk about) prototypes in 2014/15/16...
How long is the 100-400L on duty?
And still no update... (well, let's ignore the 10k$ 200-400 1.4x converter monster).
Anyway this workhorse will continue as the walkaround lens for 5D/6D and 1D-families for quite some time.
In case someone wonders what to shoot with the 24-105L, you may have look here:
http://www.ipernity.com/tag/canon/keyword/294182