I lost track of which case the court decided to hear anyway. In theory, if the court brought before it the case where the judge ruled Obamacare unconstitutional, a 4-4 tie would end Obamacare. If a different case was brought up by a Judge who upheld Obamacare, a 4-4 tie would let Obamacare stand.
I was adressing the possibility of Sotomayor recusing herself from the case.As for a possible 4-4 tie I'm not sure how the SCOTUS works...I think it might be that only a majority can overturn a law.But I'm sure that someone who knows more will correct me if needed.