Even if the short story has finally died, this does not mean it will cease to be written. You can still join a medieval madrigal chorus if you want. But without the Atlantic, if you're interested in the current state of the short story, you'll have to crouch down below the knitting magazines at Bulldog News to read a limited edition of a literary magazine.
Fiction in the Atlantic is (or was) edited by C. Michael Curtis. Curtis has worked at the magazine since 1963. During his years there he has read more than a half-million stories. As a result, the fiction in the Atlantic is idiosyncratic and funky compared to the often fashionably safe work found elsewhere. Of the few general-interest magazines that survive today, only a handful publish fiction and then only as intellectual wallpaper. A recent issue of Esquire, for instance, contained a spread on male fiction writers titled "Bad Attitudes" and subtitled "We dressed them in clothes that even the orneriest man would actually wear."
But perhaps the true loss with the eventual retirement of C. Michael Curtis will be the end of his prolific output of rejection letters. Just about every decent short-story writer I know who still bothers to send his or her stories out for publication has found a degree of salvation in his curt, specific notes. Considering that only one in a thousand stories submitted to the magazine finds its way into print, his letters provide a point of connection and sense. Rejection is still rejection, but at least it is sweet, and far preferable to its absence.