Dr. Seuss's original story was a heart-wrenching tragedy whose single ray of hope depended on the reader's willingness to commit to the cause Seuss put forward. The only reason to change its apocalyptic ending would be a steely-eyed desire to rake in a bigger box-office take. Next up from the filmmakers: a version of "The Giving Tree" with an up-tempo song number for the ending.
On the other hand, "In Time" had moments of formulaic action-flick sloppiness, but created a solidly imagined future society and delivered compelling performances and a harder-hitting element of social commentary.
I'd recommend skipping "The Lorax" and giving "In Time" a shot.