You’re kinda implying that Old Party is essentially bad in a way that New Party won’t become. That’s not how things work at all. A party is just a collection of people. They don’t go away. The system that got them there doesn’t go away.
I feel like a broken record, but God, Americans need only look beyond their own borders for just a SECOND to see real-world examples of almost every other ‘hypothetical’ posed by all the armchair political scientists in this thread.