New Zealand and India are on top in terms of performance in this World Cup. Here I was optimistic about South Africa. But their performance did not seem consistent. Because they lost against a normal team. Defeats against any team in cricket are not unusual but losing to Netherlands doesn't give me confidence to go far with them. Still I know why I think either of these two teams South Africa and Pakistan can come. There are still several games left. But your assumption definitely rational because India and New Zealand are yet to lose a single match. So they have the highest chance of winning the World Cup.
I was also optimistic about South Africa. But now I am looking more strong New Zealand team. I am thinking that the India and New Zealand will play the final match. But I may be wrong. But there are the chances of Pakistan team too. But like South Africa they also don't have consistency. So I think New Zealand can win the world cup.