Initially, they will study the case of the California ban of marriage for same-sex couples before considering the two cases of couples who are challenging the Defense of marriage act (DOMA). They will thus talk about a federal legalization of marriage equality. However, it is extremely probable that the Court won't really make a clear decision.
Anyway, it will be necessary to be patient before knowing their decision because this one will be ruled in June.
If you wish to listen or read the first hearings on prop. 8, here the audio, the American Foundation for Equal Rights put both versions on their site: American Foundation for Equl Rights