America has 313,019,553 people, Europe all up would be more. Let's say 600mil for both at a guestimate.
Thats 600mil pop divided by 2mil players = 3% of US and EU playing SWTOR.
HK and Sing together is 12mil + OZ 22,831,926 + NZ 4,437,900 = 39 mil people
39 divided by 3% = 1.3mil people
3.3 mil needed to make 5mil players, statically, they will only get 1.3mil Oceanic players. That's 3ish million TOTAL (current 1.7mil subs + 1.3mil Oceanic subs) players after Oceanic launch.
But that doesn't even take into account how many Aussies and NZ'ers are already playing.
So it will be less.