(replying here as this references an ISIS specific remark)
In Syria and other Middle Eastern countries? sure thing, because they’re engaged in a full-on war and the average Westerner never gave much of a shit anyway, which is partly why ISIS has become so big in the first place.
In Europe? I would argue ISIS is now only indirectly killing people. Partly through the effects of true ISIS attacks (those paid for and executed by ISIS terrorists) and partly by applying after-the-fact branding to other killings, they set off a chain reaction where people who are not ISIS at all, and who would have a lesser or zero chance to be activated as agents of terror otherwise, are effectively doing ISIS work, or work that furthers ISIS’ agenda if you prefer.
Obviously, media cannot NOT report on such events, but try and think of ISIS without media?
A vicious cycle has been set up, where the more terror is pumped into the media, the more people pay attention to media, so terror is features in media more and more often - as terrorism reportage and discussion gain increased media presence, the higher is the likelihood that more such events are triggered.
Most big media trends just die off, hitting the same note time and again cannot hope to achieve the same result every time, sad or not, this is the way human beings are: attention begins to wane and later desensitization creeps in. People will want to think about other things than death and the risk of getting killed by terrorists every time they leave home for work or pleasure. The media circus will want to move on to cover the next big thing, whatever gets people’s attention and piques their interest: advertisement is king.
Rather than ISIS running out of candidates, reportage on terrorism becoming more routine and less sensationalist is what I would expect.