How could a regime change in Iran affect India & be beneficial for Pakistan & China?

A regime change in Iran could affect India's usage of Iran's Chabahar Port, India's trade gateway to Central Asia and Afghanistan, and affect India-Iran bilateral trade worth $1.3-1.7 billion. Meanwhile, a Shia Iran had counterbalanced Pakistan's Sunni-majority extremist groups, with a regime change disturbing the balance. A new Iranian regime may lean towards China, Iran's long-term partner.