There is also the not-unlikely possibility that the court takes the case but then rules in an extremely narrow way that leaves open the larger question about the copyrightability of APIs.
The petition for certiorari has to explicitly lay out the questions that are to be answered by SCOTUS. In this case, the questions are: (1) Whether copyright protection extends to a software interface; and (2) whether, as the jury found, the petitioner’s use of a software interface in the context of creating a new computer program constitutes fair use.
Considering that SCOTUS is being very directly asked to rule on the copyrightability of APIs (and fair use, if they are copyrightable), not reaching the question is pretty much only possible if they dismiss the case as improvidently granted.