I think that flavour-wise, the Warforged are an awesome addition to Eberron. But we're not getting 4e Eberron at the beginning anyway, so they should wait for the PHII. Though they work so well in Eberron, the Warforged are not thematically appropriate for a large number of settings, so much so that it would be silly to put them in the PHI, in my opinion. The Changeling would be a much better choice if they insist on having a race from Eberron in the first standard PH.