India is just a pretender. They are currently 3rd in the world behind Australia and South Africa. not even second IMHO. Australia just don't drop to number 4-5 with loss of one series. In India defeated Australia in India then in the same year Australia defeated India in Australia. Add to that Australia have very good record overseas. Two away series India played in 2008 they lost. Also they drew one home series. India played 5 series won 2 lost 2 drew 1. So indias performance is  not as emphatic as you are pointing out.

But it is true that if India continue to win and Australia lose next series being played in South Africa  immidately India will become number 2 (even ICC ranking wise). But I don't think Australia will follow the path of West Indies. Australia have pretty good infrastrcutre that will continue to produce competitive cricketers in year or two.

And why would you want India -South Africa series now. India south africa played ealier this year it was a draw , last year south africa defeated india. So they are clearly head and shoulders ahead of all the nations.

Obama,

You don't need spinners to dominate the world...if you have great fast bowlers.  We have seen how Westindies dominated world cricket only because of their faster bowlers. Regarding south africa in Asia they toured pakistan last year defeated them easily in test series.

South Africa toured india. India presented them with one of the worst wicket which turned square. Still they managed to draw the series 1-1. They defeated india in South Africa.

As far as sri lanka are concerned they have not played them for a long time. So it is difficult to predict how they would play. But seeing how Sri Lanka are struggling now against team like Banladesh, I think south Africa will at least draw the series in Sri Lanka unlike India.