Deep Wang posted presales from a theater chain for bigger movies on BOT forums and he's moving on to another job, but here's the latest on Black panther and how it compares to other big marvel movies:
https://forums.boxofficetheory.com/topic/24007-the-box-office-buzz-and-tracking-thread-electric-boogaloo/?do=findComment&comment=3370950
Total presales the same number of days before release:
$6.941m - Black Panther
$3.394m - Age of Ultron
$3.208m - Civil War
$2.345m - GotG2
$2.106m - Ragnarok
Plus other charts at the link. Pretty crazy stuff, the upper limit for this movie is very much open ended.