So did jack indirectly erase all his friends from the future.
After all despite Aku being evil the world was realy technologically advanced and a lot of races came to live on earth for some reason or other.

If jack erased Aku from history than is it possible all of the people he helped will never even be born because he drastically changed history.

Personally i think the ending where jack somehow defeats aku in the future and just accepts the fact this is his world now and the past is just the past would have bean better.

The ending we got felt like the kind of shit designed for the widest audience possible.