Assuming Bangladesh will make it to Super Eight, it's true that the winner of SA vs Aus and NZ will have a big advantage going into S8. They will start with 2 points and will face both Ireland and Bangladesh in the S8.
So NZ and either SA/Aus off to 6 points; they'll be hard to catch for the others. Especially if India qualify instead of Sri Lanka, in which case Bangladesh will start at 2 points and the gap between NZ & SA/Aus and one of the other main contenders (i.e., India) will be even bigger.
So, into the semi-finals: NZ definitely, plus the winner of SA vs. Aus. Come to that, the loser of that match will probably make it to the semi's anyway given the quality of the two teams. That leaves WI, England, and SL or India as possible fourth semifinalists. If SL qualify, it could be a tight race between them and WI. If India qualify, I guess the 2 point gap with WI going into S8 will be decisive.
Of course, this all changes should SL and India both qualify (i.e., a really poor performance by Bangladesh against Bermuda happens) or England somehow manage to pedal their way into the reckoning.
Whatever happens...at this moment in time NZ, perhaps surprisingly, are the best placed team to make it to the semifinal. Tomorrow we'll know whether they are joined by the #1 or #2 team in the world.