Do not get sudden excitement by a falsified population figures given in the first paragraph. When corrected you will see that the rate of increase of Hindu population is much slower than the Muslim population. The total Hindu number has not decreased that much. Refer to the short table given in the article. Consider 1951 base period when the total BD population was only 40 million of which Hindu population constituted 22.0%. It means Hindu poplation then numbered 8.8 million.
In every census since 1881 one can see Muslim population increased faster than the Hindus. So, if today the Hindu population is at 8.5 million, it can be said that the Hindus took less number of children than the Muslims. So, for the progressive minded Hindus they have almost reached a stage whereby their population has stabilized at this figure. I would not say there was no Hindu migration during this 60 years. However, it was not substantial. It is because there is no religious persecution in Bangladesh.