What is the Drupal 7 version of FILE_STATUS_TEMPORARY?
That is strange, as FILE_STATUS_PERMANENT still does exist indeed. But the value of FILE_STATUS_TEMPORARY used to be 0. So I suppose you can use anything that evaluates to zero: FALSE, NULL, 0. Personally I have always used 0.

But why set your file back to temporary to have it deleted by cron, why not just delete the file directly after processing? You can use file_delete() to do that.