Given in the last week VIC has only had 3 mystery cases, NSW has had one, surely opening VIC up internationally would be on the cards as well, obviously not at the same time but not too far behind.
That is entirely up to the Singapore government. I live in hope that by early January that it will be. But I think the government here is just looking at spread (regardless of linked or mystery cases) happening within the broader community (ie excluding international arrivals), so the daily cases - and total number of active cases in VIC - is the critical metric for them.