I learned something interesting about this in religion at my Catholic highschool (I'm a sikh btw,not to be confused). So if I'm not mistaken,Christians believe that god will bring the kingdom of heaven down to earth,when Jesus is to return for the second coming,right?Well it's interesting because sikhi has a similar idea of khalsa raj,where we believe that the khalsa or the "pure" will rule the world after eliminating all tyrants and evil in the world.I always wonder how all religions and people will coexist when the time finally comes.
However,to clarify our gurus won't "come back" per say, because they're already here in physical form and have been in physical form since 1469,the birth of our first guru.Our current guru,the guru granth sahib is eternal and a living embodiment of our 10 gurus.It's not really a holy scripture,but actually our living leader/guide in these dark times of ignorance and illusion.We don't accept that evil rules this world,but rather in this age of kaljjug,the forces of evil have a much stronger influence than other ages,in fact the strongest of them all.I think god has kind of taken a step back where he's letting all sorts of heavy sins run rampant without smiting the sinner on the spot,but the door to god remains open for those who seek it.Note-for us,god is omniscient and omnipresent,so it's not that God is separate from the sinner,but rather the sinner is unaware of his true self.So in this crazy world where everyone sins,a very few become one with god through intense devotion,and it is these self realized people in the form of god who ultimately rule the world in the background,not evil.God has the power to instantly merge everyone within himself and clean the world,but it's their play and they can do whatever.It's not really for us to understand why god doesn't simply merge us back with himself and end all suffering everywhere right now,nor is it our job to worry about how or when that will happen.It's hard enough as is to be free of evil and sin even with the company of others who hope to walk this path on forums like these ,so we should instead focus on walking on our paths.
Another thing I thought about,imagine the happiness in the world where finally for christains after thousands of years of waiting and for us,hundreds of years of brutal torture and war,the day when this will finally happen.