In two episodes of the Ben 10 series, we are introduced to a future setting. Both in which a verion of Ben Tennyson is in.
In the first future episode,Ben 10,000, Ben and Gwen Tennyson are taken 20 years into the future by Gwen's Future Self using a spell, and it it up to ben to stop the combined forces of Dr. Animo and Vilgax.
In the second future episode titled Ken 10, future Ben is 45 and has two children, one of which, Ken, is having a birthday. So it is up to Future Ben and Ken to save the world from Kevin 11,000.