If one day the creators and developers of any of these currencies die or bancrupt, what will happen to the currencies? What will happen to the coins we have? Are the coins we have still worth anything?
I don't think that all creator and developer will go because cryptocurrency is too worth if they're leaving the crypto. But if that thing is happening, then the coin will not have support from the creator and the developers, and the coin will be abandon by the people too. The coin itself will die and disappear from the market without any chance to rise back. The coin will not worth in the market, and it will be delisted from all of the crypto markets.
In the case where the project fail or go bankruptcy, then the project will slowly be dying down because there would not be any push for it as the team that were in charge also would have withdrawn. It boils down to why we have people always advising about knowing the team too well before relying n a project for a long term investment, only a solid team will never give up on a project.