AFAICT the installed binary is called startkde4, not startkde:
Index: pkg/README-minimal
===================================================================
RCS file: /cvs/ports/meta/kde4/pkg/README-minimal,v
retrieving revision 1.2
diff -u -r1.2 README-minimal
--- pkg/README-minimal 15 Jan 2014 15:36:25 -0000 1.2
+++ pkg/README-minimal 23 Jan 2014 16:54:02 -0000
@@ -23,7 +23,7 @@
Then the following line should be added:
- exec ${LOCALBASE}/bin/ck-launch-session ${TRUEPREFIX}/bin/startkde
+ exec ${LOCALBASE}/bin/ck-launch-session ${TRUEPREFIX}/bin/startkde4
... in ~/.xinitrc when using startx(1) (console login)
... in ~/.xsession when using xdm(1) (X Display Manager login)
