We've been to WDW in the first part of September for three years in a row. Sept 2000 there were e-nights the entire stay. Sept 2001, there was three enights scheduled, but only one took place, the other two were canceled. Sept 2003, there were no enights scheduled. I doubt you will see enights in September any time soon. It's not really needed, except to see MK in the dark. It usually closes at 7, except for Sat when Spectro and the firworks run. Maybe late September they will add an enight. But, I know around 9/11 the crowds are non-existent, so it is easy to get all the touring in w/o enights.
Good luck and I hope you get your enight. I've stopped holding my breath for any, at least in the first 1/2 of the month.