To be quite honest, SCOTUS refusing to hear the case, if such a case ever came their way, is something I have never considered happening. How do they decide which cases to hear, anyway? I seem to recall that they turned away one or two high-profile cases last year.
The only thing holding Roe v. Wade in place is precedent. That's only a legal guideline, it isn't legally binding due to contradictions in precedent in other court cases. The SCOTUS never wanted the can of worms by countering the precedent IMO.