Even now there is a reserve day. Perhaps if the semi-finals are affected by rain, the matches will resume from where they left off the next day. If there is rain on the Reserve Day as well and the match is not decided, the team with the most points at the end of the league matches will be declared the winner.
The same is true for the final on November 19. There is also a reserve day if it rains. As the Indian team has won all the matches in the league matches, if it rains on the reserve day as well, it will be favorable for India.