To be fair, CSJ and the SDP have always been in favour of opposition unity, because that's the only way to defeat the powerful incumbent. If you remember, prior to GE2011, in late 2010, he extended an invitation to all the opposition parties to a meeting to discuss a loose alliance for the GE, but got a lukewarm response instead and the initiative fizzled out.
A fragmented opposition is exactly what the PAP wants, and until all the opposition parties pool their resources and work together, I don't see an opposition government - not even a coalition - after GE2016.