SO IN CONCLUSION, The drop will be anywhere from 15 - 25%, anything below 15%, will guarantee 100M this weekend IMO. However, less than 20% doesn't rule it out.
I don't recall a movie dropping that high in mid - June. Man Of Steel dropped 21% on Wednesday. That was considered a bit high but it went against NBA finals.
Not to go off-topic here, but please find the time to read Shawn's new article at BO.com regarding Batman Begins and how it really started the "reboots" of today.
http://pro.boxoffice.com/latest-news/2015-06-16-begins-turns-10