First, it is not the T20 World Cup but the World Championship.
It begins in earnest on March 15 and ends on April 3. Before this there are the qualifying rounds (which also rank as T20Is and World Championship matches) from March 8 to 13.
In these qualifying matches we have:
Group A: Bangladesh, Netherlands, Ireland, Oman
Group B: Hong Kong, Zimbabwe, Afghanistan, Scotland
The winner of Group A (probably Bangladesh) joins the big boys in Group 2. The winner of group B (probably Afghanistan) joins Group 1.
So we have the Super 10s in
Group 1: England, West Indies, Sri Lanka, South Africa, Afghanistan(?)
Group 2: India, New Zealand, Pakistan, Australia, Bangladesh (?)
My prediction for the semi-finalists are West Indies, South Africa, India and New Zealand. Many may not agree with this.
On current form, India would appear to be favourites for the title.
Anyway, for the general history of the T20 championships since 2007 you can see:
For the last championship in 2014 which had a similar format:
Schedules for the 2016 championships can be seen in Cricinfo or here:
It is not clear what will happen if Pakistan pulls out for some reason. But it is unlikely that they will be replaced by another team.
You can also amuse yourself with the ICC T20 rankings as on March 6 (after the Asia Cup and two matches between Aus and SA):
A related post: