First off, as others pointed out the technology will improve. I think one day it probably will replace human audiobook readers. I listen to a lot of audiobooks. Unfortunately, the quality of the performer has a LOT to do with the experience of the listener. Take for example Frank Muller. He was widely known as one of the "best" audiobook readers in the business, his career ended only by a tragic accident in 2001. I knew of him because he read almost all of Stephen King's audiobooks. While I feel for the man and his family, I have to say that I found him unlistenable. I bought a recording of Black House and could not make it past the first half hour. He read things in an overwrought, almost Shakespearean tone, even for mundane bits of narration. And every sentence had the same basic pitch structure. It made me laugh, as well as everyone I played it for. The part that made me stop laughing was that I'd paid $60 for something I couldn't listen to.
Clearly he has plenty of fans, what with all his awards and accolades and such. But he was not my cup of tea. This is unfortunate, as I'm a King fan. Even if I've read a book, it's nice to go back and listen to it again later on audiobook while driving or working out. After Muller had to retire, George Guidall performed the rewrite of Gunslinger. I was dismayed to realize he used the exact same performance style. Since then I haven't even tried another King audiobook. Considering the quality of his more recent output, this hasn't really bothered me that much.
And then you get older or more obscure titles that no one is going to perform because of the costs involved. Or titles that were performed long ago and you can't find them anymore. I recently found a torrent of Heinlein's Time for the Stars. I enjoyed the story quite a bit, even though it was a fairly lousy quality copy of an old cassette and the performer was nothing special. The only other way you're going to find this recording is eBay/craiglist/garage sale.
On top of this, places like Amazon and Audible frequently don't even list the performer. I'd say "usually", in the case of the titles I look for. And when they do and it's a person you've never heard of (also frequent), good luck finding a sample of their performance.
So yeah, I see a huge market for something like this if they can improve the technology enough. Audiobooks are insanely overpriced, and I wonder what using software like this might do to that price. I would hope that there'd still be a market for certain performers, like Jim Dale. His Harry Potter performances are wonderful. And I'd miss hearing the works of Sarah Vowell or David Sedaris in any voice other than his. Of course, eventually it's likely that a computer simulation will be able to mimic them fairly accurately. I know I can already mimic the latter two in my head when I read their writing in print. Imagine if you could get the works of Twain read in a sufficiently Twain-like voice. Or set the voice to "James Earl Jones" when you listen to Lord of the Rings.
The authors have nothing to worry about. In fact, they'll probably make money on the deal. It's the performers and those who work in the recording department who are going to be out of a job. But then, they'll be jobs created for software people. Such is the way of change.