Unless my understanding of what a CIQ/ferry entails, unlikely going to happen.
SC is gated and guarded right at the entrance. Doesn't make sense to build a CIQ at the Marina area to service only SC population of (how many) currently? Sure, new developments are coming up but it'll be many years before you see the population increase...even then, to service only SC population may not be viable. To open it up to public, also not viable cos that will defeat its gated and guarded concept.