The USSCT can do it whenever they want, I think they realize how important this is for the nations US Housing Finance Plan.
But I don't know how long decisions are made after Oral Arguments are made. I think it's 1 or 2 weeks after conferences are held and usually sequentially with Oral Arguments.
Since the case sat a year in limbo I believe the decisions have already been made and oral arguments are merely a formality at this stage of the game as SCOTUS has prepared to scorch the earth :-)