How is the new anti-conversion law going to affect Christians in India?
The real short answer is that Christian Churches will adopt to the situation as they always have.
Churches will continue to survive regardless of how legally they are mistreated in any time or place.
To give you an example, I would like to mention with happened in Japan between 1614 and 1865.
The Year of Our Lord 1614 brought a harsh reality to all Catholics living in Japan. That year the Japanese government expelled all priests and bishops from their territories.
Normally one would think that without any clergy to attend the faithful, the faith would die out. But the opposite happened!
Catholicism without priests
The government must have been just as surprised as Father Petitjean when tens of thousands of hidden Christians came out of the woodwork after that remarkable 1865 encounter in Nagasaki. These people weren’t supposed to exist, and yet here they were, telling stories of secret baptisms and Marian images made to look like Buddhist goddesses. They recited “Latin” prayers that were barely intelligible to the western priests and sang hymns modeled on Buddhist chants as another layer of camouflage.
But they had appointed men as catechists, men to baptize and serve in a pastoral role, and others to keep the calendar. They abstained from meat on Fridays, observed Lent and Easter, even attempted to celebrate feast days. As best they could, they gave their children Saints’ names. Many had resigned themselves to the need to deny their faith publicly, but they prayed acts of contrition, again and again, longing for the day when they would once again be able to receive sacramental absolution.
They knew the priests would return. They knew because the missionaries had promised, and they knew because a martyr named Bastian had prophesied in 1660 that after seven more generations, confessors would return to Japan. So they counted down the years until that fateful day in 1865 (seven generations later) when Father Petitjean received them at the church named for their ancestors.
In 1614, all Catholic missionaries were expelled from Japanese soil. Fr. B. Petitjean arrived in Nagasaki, Japan in August 1864 and was able to construct a small Church. On March 17, 1865 he discovered that the Christian faith had survived in Japan for some 250 years without any missionaries (priests) to administer the sacraments!
In Japan March 17 is liturgically celebrated as the Finding of the Japanese Christians*. Sorry, St Patrick's Day is not a big thing on this day in Japan!
What is true about Catholics adopting to harsh political situations is equally true for other Christian denominations and traditions.
In communist countries, I know of both priests and pastors who work in rice fields (or other areas), in order to administer the sacraments and teachings of the Gospel, without the governmental authorities being any the wiser.
Churches, whether Catholic or not will always adopt to the political situation in whatever circumstances they find themselves.
As for the new anti-conversion law being considered in India, it is too soon to know how to react.
Some Christian leaders will definitely go the political route and challenge the law in court.
The new anti-conversion laws may only affect forced conversions in one form or another. This would have little impact on conversions freely done. The law must be defined and take affect first. In any case, many Christians are thinking, I am sure, of how to react to this particular situation.