SIA can't replace a 180-seater with a around 300-seater which the B777-200 is. And a B777-100 is not in sight any way.
Why not choose A330-200s? It offers not that much more capacity, and that difference can be neutalized by the A332's high economic performance. It can fly short haul as well as thin long hauls, and not a single pilot has to be trained a lot for it: As the A340s are going to leave, those pilots can change on the A330, maybe with a three-day training.
Not to forget the A330's high comfort level. I hope we see a SIA A332 soon.
Me & You & a Plane Named Blue...