We know what people in the 20th century thought the 21st century was going to be like, but do we have any sources or documentation or books that attempt to describe the future (preferably the one we're living in right now) by medieval writers?
No. Looking to the future only became interesting when science made that possible. So it possibly started when the early enlightenment took hold. Very likely much, much later, after the industrial revolution.
Medieval society wasn't static, but pretty close to it. Most certainly from our modern point of view. Looking to the future, I think, really took of when Jules Verne and other writers in the 20th century started to extrapolate science to the future.
Take for example fashion. That can change, now, pretty rapid. What was fashionable in the sixties looks pathetically old to us. In medieval society fashion changed too, but that took many decades. It wasn't unusual at all to inherit clothes from your grandfather which you could wear without any problem being out of fashion.