Re: Replacement of A310s.
From what I am aware, SIA considered several options. The A332 was one but it was dropped because its range was too long, wingspan too wide, and overall it was too heavy an aircraft to do regional routes. Airbus offered the proposed shrink A300-500 but SQ was unimpressed, much for the same reasons. The A321 was considered but it was dropped because it was a narrowbody. I'm not sure if the 767 models were seriously considered, but SQ never purchased the earlier 767 models partly because their ULD configurations were not compatible with SQ's hub operations at SIN.
SQ already has the first four (9VSMA-SMD) on the market and you can expect them to try and downsize the fleet in the next few years, either by sales or leases. A number of their 744s are leased, so they have a relatively easy way to downsize the fleet if they wish to.
Re: Route Expansion
SQ launched two North American routes (SIN-AMS-ORD and SIN-HKG-LAS) in relatively quick succession, and Baldy (whoops... Dr Cheong) has publicly stated these will be the last new North American destinations for some time. SQ's current focus will be to make these two routes profitable and concentrate on the launch of nonstop A340-500 services, initially to LAX.
SQ has always had a "fantasy" route to Brazil via South Africa, but I don't see this materialising anytime soon.
Re: MAS/JAL to South America
No way MH's route is making money at the moment, not with Argentina's current economy. JAL has flights to Brazil because there is a huge ethnic Japanese population there.
I know this is slightly off topic, but when I was with SQ we had a fair number of Chinese passengers - usually all male groups - travelling from China to BKK on a Chinese carrier, BKK-SIN-KUL on SQ, and then KUL-EZE on MH, with an onward connecting flight to Colombia or Ecuador somewhere like that. Their travel documents were always in order so we had no reason to refuse carriage. Our suspicion is that they were being smuggled into the US via South America. I used to see at such groups at least once every two weeks. It's a horrible feeling to see these folks being smuggled and being powerless to do anything about it.