both ishant and sree have lost quite a few k's. ishant used to bowl in the low 140's and sree in high 130's. may be they will go back to those speeds in more conducive conditions. zaheer has slowed considerably with age. he is past 31 now. he used to bowl at mid 140's for the first 3-4 years of his career.
expect rubel and shafiul to add around 5k's when they bowl in SA or oz.
sri lanka's fastest bowler at the moment is dammika prasad who bowls at high 140's, touching 150 now and then, on sub-continent wicket no less !!
in the sub-continent, purely in terms of pace
SL> other two
BD>=Ind (as long as rubel plays)
Anything can be sacrificed for truth,
nothing is too valuable to sacrifice truth instead.
-- Swami Vivekananda