They may pull it off. Or they may be content with striking terror into the hearts of the enemies of Allah (cf. Qur’an 8:60), by means of the threat itself.
“PHOTOS: ‘ISIS’ Promises Attack on Rio Olympic Games 2016,” by S. J. Prince, Heavy, August 6, 2016:
A since deleted Twitter account by Islamic State sympathizer Abu al Abdel promises that the “Islamic State lions” will attack the Olympic games in Rio de Janeiro, Brazil. Yesterday, Islamic State terrorist channels on the encrypted messaging app Telegram were reminding would-be jihadists that it was the opening ceremony of the 2016 Rio Olympic games. Rita Katz, founder of Site Intel, reports that Islamic State is instructing its followers on how to attack the games. Katz further reports that ISIS is telling jihadists to become “lone wolves” and “obtain guns or cause traffic accidents” and to attack public transit, take hostages, and to stab or poison people.