@wlakshmikant,
I think I understand what you are saying. Yes, master re-election will occur (upon powering on the stack) if you add a new switch while the stack was powered off. However, there will be no re-election if you add that switch while the stack is up and running.
Think of this as OSPF DR/BDR/DROTHER election/re-election on multi-access network.
Please @lagapidis, correct me if I am wrong, I want to master these concepts. Thanks