A search for "// Copyright (c) 2009-2012 The Bitcoin developers" gets 54 hits in the codebase. Most of these files seem to have been touched in the past year, so that might warrant their update.
Is there any reason not to bump to 2013? If not I'll put in a pull, and when 2014 rolls around.
We had that discussion some time ago, I'm not sure about the consensus. If I remember correctly we don't want to update ALL copyright strings, new files should contain a current year, the client meta-info needs to be current...
In principle, people that update an implementation file should update the copyright notice.
So if the file is touched for non-trivial reasons this year it warrants extending the copyright for that file to 2013. This must be considered on a per-file basis, so substitute-all commits will not be accepted.