This doesn't appear to be one of the variations listed at Alternate Universe so...
Bad future is one of the more common Alternate Universes
, in this praticular variation the heros are sent into the future, and while they were gone the villain(s) took over. 9/10s out of 10 the hero will meet La Resistance and/or aged versions of his friends who were left in the past, the plot typically ends with the character going back in time and stoping it from ever happening.
Sonic CD, where the name comes from
Kim Possible did this in The Movie
GI Joe did this once, for more info see Rushmore Refacement