It occurred to me that Geert Hendrickx wrote in gmane.os.netbsd.devel.packages:

> It seems to work quite well.  I tried the program on a non-trivial pkg tree
> (only to-be-updated packages are shown in the graph), and the resulting
> script looks fine (correct build order).  
>
> http://lori.mine.nu:5190/geert/pykg_upgrade/

Hm, I'm not too sure I agree on the 'correct build order' thing. Using your
example, as I accidentally updated my own system just yesterday, using
wip/pkgmanger:

echo 'kdelibs 3.4.1 => 3.4.1nb2'
cd /cvs/pkgsrc/x11/kdelibs3 && make replace || echo 'Failed at kdelibs-3.4.1!' 
[..]
echo 'pcre 5.0nb1 => 6.2'
cd /cvs/pkgsrc/devel/pcre && make replace || echo 'Failed at pcre-5.0nb1!' 

kdelibs depends on pcre, yet pcre is updated *after* kdelibs. 

One other nit: It doesn't clean up after the job.