Webkit 1.4.0 is out as stable upstream and all deps could be met with what is in portage (unstal libsoup etc). I suggest putting it into portage as unstable.
*** This bug has been marked as a duplicate of bug 366943 ***
I reopen this bug. For almost a year the repository holds a buggy, old version of webkit although a new version is readily available. This is not an acceptable state, gtk-3 overlay or not, webkit-gtk-1.4.0 belongs in portage.
If you have a problem with current webkit-gtk in tree, just fill a bug report about it. *** This bug has been marked as a duplicate of bug 366943 ***