> After the SL test win, does IND go up to No. 2 in the ICC rankings OR do
> they have to win the series for that
Nothing changes mid-series, thus India is ranked three at the moment.
For India to overtake England at the end of the Ind-SL series, they require
only a draw in the final match. A 1-0 series win would improve India's
rating to 113.44, just sufficient to pip England's current 113.40.
Obviously a win to India in the third Test against Sri Lanka would make the
margin more clear-cut.
> If AUS somehow loses to SAF in the test series;
> and IND beats ENG and PAK in their forthcoming series;
> then IND may be No. 1 in the ICC rankings
Yes, it's possible.
If India defeats Sri Lanka 2-0, then beats both of Pakistan and England 3-0,
they will finish the series against England with a rating of 123, which
would take them to number one if Australia loses its home series to South
Africa by at least two clear Tests (i.e. either 2-0 or 3-0):
India (2-0 v SL, 3-0 v Pak, 3-0 v Eng): 123.11
Aus (0-2 v SAf): 122.63 or (0-3 v SAf): 121.57
Of course by the time Ind-Eng finishes, the return SAf-Aus series will have
started, and on completion will change the figures again.