If I think practically, as per team's form is concerned, I will go for below 4 semi-finalists -
PAKISTAN
AUSTRALIA
SOUTH AFRICA
SRI LANKA
Out of these, only 1 is unpredictable i.e. India Vs Australia. If Sachin, Zak, Yuvi, Bhajji, Ashwin together will have a best day, then Australia might lose it. But if Indian batting woes continue in death overs, then it would be very easy for Watson & Co. to reach the target easily.
South Africa will choke but not against New Zealand, they will be out of the tournament in Semi-Final.
Other two will be the easiest QF. West Indies can't beat Pakistan if Gayle and Pollard goes early, even if they got the target of just 200. Sri Lanka will exploit England easily with spin power in Colombo.