What if all the characters survived?
 

What if all the characters from harry potter survived? What would it be like now??

They would still be at war.

I'm inclined to agree. Given how stubborn and hungry for even more power Voldemort was, I don't see him humbling himself enough to be a good guy. Even if he and his followers were put in a wizarding prison, it could be only a matter of time before a few broke out and the entire war cycle started again.

Yes, there is that, but there is also the real life example that war is inevitable. There will always be two factions at odds with each other. Just as you had Grindlewald before Voldemort, there would always be somebody to fight. So, there most likely would have been multiple factions growing that we weren't even aware of.