So...I thought of this in the car on the way to school
After the Paladins defeat Zarkon, there is a joyful celebration. The Paladins return to Earth and reunites with their families. But it doesn't end there.
Each of the Paladins sneak during the night to a secluded area where they meet up with their lions, and they all meet up with Allura and Coran, and the other aliens and allies. So basically Allura, Coran, the Blade of Marmora, etc. visit Earth from time-to-time. Allura and Coran decide to live on the moon, and everyone is happy and living a normal life again.
And then there's Lance, Hunk and Pidge with humongous stacks of work they missed at the Garrison, but they don't have to do it because they saved the universe.
And then sometimes they all have fun by racing each other in the lions in outerspace near Earth, and they all end up going on adventures and stuff with their families and all that.