It does NOT amend any existing legal provision which enables any foreigner to apply for Indian citizenship through registration/naturalisation.
Many of them are from majority community of these countries.
E.g. 4.61 lakh Tamils of Indian origin were given Indian citizenship during 1964-2008.
It only provides a mechanism for some migrants who may otherwise have been called “illegal” depriving them of opportunity to apply for Indian citizenship provided they meet certain conditions.
Therefore, there is no question of any influx of foreigners swamping the indigenous population.