It does not necessarily mean the issue "returns to the states". The USSC could totally federalize the question. There are a number of methods for doing that and sound arguments behind them.
federalize? by judicial fiat? I have heard Scalia comment on that - he is against Roe, but he has been clear to say that if the people through their legislatures want abortion (some), they can have it.
you will never see a SCOTUS conservative enough to use judicial fiat to rule that an embryo is a person with constitutional rights that no state can abridge. you could get such a ruling on late term abortion, because medical science can validate the child is viable outside the mother, but not for an non viable embryo.
in any case, for those here who want to change the subject - I am still fuming over the ports deal.