So I was wondering in the horrifying situation that our beloved Queen Chrysalis were to be killed somehow what would happen? Would the hive die off or would another changeling be made into a replacement?

I am kind of curious to hear all your theories on this matter.

4927870
Well, my headcanon is that Queens come about when a changeling starts leading a large group of other changelings. This changeling mare will then slowly begin to grow into the special biology of a queen changeling and a hive mind will develop in the group with the new queen as its head. After the transformation is complete, the queen then stops aging, and is not capable of succumbing to old age.

So if our queen were to die, another would arise in time. Weather or not the hive would remain united, is the real question.

There is no actual canon though about that sort of situation though, so this whole thing is just a reason for everyone to state their headcanon.
You have one?

4927893 I was thinking along the line that the Changeling hive would have something similar to bees called Royal Jelly, which could convert a youthful changeling's genetics so that he or she would gain the traits required to lead the hive. Being resourceful it would make sense that Chrysalis might have some stored away for safety in case of such an event. But that is just a theory.

4927870
I a headcanon that she got a nephew that can take her place. His name is Prince Kevin.

4927959 Why does changeling royalty always crash weddings?

4927870 I have a headcanon that the changelings that want the position of a King/Queen ask from three ancient rulers of legend for the blessing to become one.

https://www.facebook.com/DarkKnightsOfQueenChrysalis/photos/pb.341583632602342.-2207520000.1450444546./892775867483113/?type=3&theater

Here I have made a headcanon post on the matter. I am of the opinion that the crown is a sacred relic, a link to those three rulers that can grant those worthy enough the strength to... "ascend" per say. It grants them the power to defend the changelings in grave times of need and is invaluable. Any unworthy bearers will be zapped to back and even go mad should they insist being stubborn about it.

If you have any questions you can just ask me.

4927870 My headcanon is that when a ruler's rule ends in some way, they are replaced by one of two options: A changeling chosen by the ruler to be their successor (Usually a biological or adopted child), or, if the prior is not available, a changeling chosen by the subjects.

On another note. Do anyone have any theories on how a pony might become a changeling queen. Is it possible or not? Would they have to be mutated somehow into a changeling (or something like it) or not?

4930992 well it maybe possible they just need asked and they reallynily accept you as thier new queen or king for you to lead them to victory.