The path for black-and-white is clear, and I can see the issues with color-negative, but I feel there is a market for slide film that isn't fully serviced yet. To think the film market will ever be like it was is a mistake; the people that will make up the market of the future are not like the people that made up the market during the 80s and 90s. (The majority of) People getting into film today aren't adopting it to take better pictures, or to replace digital, they're doing it for nostalgia, novelty, or 'authenticity'. Take a look at the return of other analog mediums. New-pressed records are largely not the music of the generation that grew up with them. Also look at the rise of subscription box services; certainly some of the success can be attributed to the gratification of getting something by snail-mail. This is where I think slide film has an edge over color-negative film, but first a couple anecdotes.
At Canadian Thanks Giving this year I brought along my Instax wide with 3 packs of film. As a side note, everyone thought it was a camera from the 70s, because even with the popularity of Instax, I was the only one in a group of 20 that had heard of it; it was always referred to as a 'Polaroid' camera. By the end of the night I had a pocket full of photos that I spread out on the table for every one to take home, and I can be sure the excitement around the table will top anything that was felt when viewing photos from the same night on Facebook the next morning.
On a recent trip home, after purchasing an Ektapro projector, I started testing it with some of my parents' slides from the early 80s. This turned into 4 nights of my family, and a few friends with no investment in the images, sitting around a slideshow typical of the 80s for hours. The comments were often about how interesting the process of viewing a slide was. I can guarantee there would have been far less engagement had I projected the same images from my laptop.
There is something to be said for the process that film images go through, and how people perceive that as a benefit. This is where I feel slide film has an edge over color-negative in today's market. Color-negative had the advantage when film was the only method of photography; it made sense, easy, fast prints. Like tedr1 said, digital has taken over this market, and does a far better job at it. Slide film, on the other hand, has that element of authenticity and novelty of being projected, and being able to see your image in true color on the film. I'm sure the argument will come up about color-negative's improved range, but like has been said, those of us using film for its image quality are the minority; just look at the rise of Lomography. We've been sold on it, so there's no point marketing to us. Film and developing prices being equal, I think we would have seen color-negative emulsions be discontinued like positive emulsions were.