Future Jessie is a character that appeared in the episode "The Jessinator: Grudgement Day". She is Jessie Prescott from 60 years in the future. Even though she is older, she was still tough and fresh. The fact that she got an eyepatch was in a sewing accident.
In the episode, she warned her present-self about what was going on in the future; Bertram-bots were trying to taking over the world. However, it turned out that Jessie and the others were already stuck in the future; by meeting their doom from a cyborg version of Mrs. Kipling. After Future Jessie rescued them, the Bertram-bots then captured Future Jessie, they set out to the apartment building to rescue Future Jessie and take down the power source in order to defeat the Bertram-bots for good. In the kitchen, they found out that Bertram himself was responsible for the chaos. After the final battle, future Jessie bidded everyone farewell and told her present-self that Emma was the one that invented time-travel.
However, it was just a story told by Ravi on what would happen if Luke made purple paint explode on Bertrams kitchenwares. It is unknown whether the Jessie in the future was real or not.
The fact about how she came from 60 years in the future meant that Future Jessie might have been 79 years old.