they knew damn well that would leak to the internet and anyone who thinks they seriously didnt think it would is plain stupid

oh hey lets get a room full of geeks together and show them a teaser to a sequel of one of the best action films last year and tell them to show noone

they know this leak would give them what amounts to free mass marketing when it hit the web. if they really didnt want anyone seeing it they would have either not shown it or simply confiscated all recording devices before showing it.