SAS actually had announced the opening of CPH-SFO in late 2008. However due to the financial struggle of the company, it was cancelled again. CPH-SFO has been on the shortlist for a decade or so, and my guess will be that SAS will open this route as soon as/if the company finds financial stability again.
SFO is according to my sources in top-3 of largest unserved destinations out of CPH, so the potential is definitely there.