The only reason I'm even thinking of going is because I want to party all night at the Mad T Party.
Also, according to disneyland.com, DJ Wendy (from the Mad T Party) will be in front of the ESPN zone from 11 PM till 4 AM. So people will be able to party, even without paid admission to any park.
Source: Park Hours & Calendar | Disneyland Resort
EDIT - link to facebook post from Disney: https://www.facebook.com/DisneylandG...99030450130061