It will happen, if there's a market for it.

SFOSIN is already starting by UA, and that's even father than YVRSIN

SQ can't fly anything because they planned poorly and didn't order at 787s at all. UA is going to eat them alive because no one is going to fly SFO ICN/HKG SIN instead of the nonstop.

It's a matter of having the right aircraft to make the route profitable and work. SQ doesn't have it, but AC does.