It's a bit hard to say for sure as the article isn't terribly clear, but what I think they're saying is that there is a dust cloud to the upper right side of the Pillars (as viewed in the photo.) They further say that the dust cloud shows evidence of a supernova shock wave passing through it, presumably from the upper right and presumably from a supernova. (Note that the supernova was not observed, and they don't report on a remnant being visible.) Then they say that when that shockwave reaches the Pillars, the Pillars will be destroyed. They estimate that that will be observed from Earth in the next thousand years or so. (Note that they don't report measuring of the speed of the shockwave -- I'm guessing they assume it's moving as typical speeds.) Since the Pillars are about 7000 light years away, than means that this destruction "already" has happened.
There's nothing impossible about all this, but it looks like speculation based on limited actual facts. It's also worth mentioning that what you see on the web went through a press office, and press offices are paid for doing publicity, not for doing science. The quality of what a press office posts (already undermined by being a popularization, which is hard to do well even when you're trying to be accurate) is frequently biased by a publicity-at-any-cost attitude. Always read press releases and the like with your sceptometer turned up to High.
Personally, I'd like to see stronger evidence for the existence of the shockwave, and evidence that the shockwave will actually disrupt the Pillars. (The Pillars are considerably denser than the medium around them, and so may be resistant.)