Anime & Manga In The Future

Ever thought about making a manga or anime about a story in the future?
How would plan a story line about something in the future?
I have been thinking about one like Pok'emon 5000 all new type of pok'emon
all new trainer and new villians, 5000 years in the future, I was even thinking of one about another called Atomica this is 6000 years after Lunar 2 the city of Atomica is a very powerful city in the future, and a very power high ruler.
So tell how would plan a story line about future of anime or manga
it can be after your favorite anime or manga.