First, a bit of background on where I'm coming from. I am currently unpublished either by traditional or self-publishing methods, but I am planning my submissions for traditional publishing houses. I am not planning to self-publish in the next few years. The main reason for this is I want exposure.
Of course, many self-published authors make good sales. Amanda Hocking and JA Konrath are the prototypical examples of this. If we eliminate the authors that were previously traditionally published, such as Konrath, we can cut this number down quite significantly. I don't have figures (what, you want me to provide evidence to support my conclusions?), but off the top of my head I can count all the new, successful self-pubbed authors I know of on one hand. That may be saying more about my knowledge of the industry than anything else, but in a way, that's my point.
Most readers still buy books from traditional publishing houses. I've seen a bunch of different numbers bandied about, but most agree on this. Whether they buy print books from brick-and-mortar stores, Amazon, Book Depository or ebooks from any online seller, readers buy books from traditional publishers. Especially the Big 6. The big publishing houses have the muscle to edit the book, slap a good cover on it and get it where it needs to be: under the noses of booksellers and readers. Though the royalties per book may be smaller, and authors have less control over the process, those are the authors that have the best chance of decent sales. For now.
I'd have to be a blind hermit to not see the changes in the industry. Big bookstores are struggling and collapsing, ebooks are on the rise, online retailers increasingly becoming dominant in the marketplace, publishers are restructuring. Many predictions are being made, and it's hard to know who to believe. Personally, I'm with many of the blogging agents who don't think the end is nigh. Some publishers and booksellers may struggle, but the entire traditional publishing model won't collapse. It will adapt. Perhaps the small and mid-sized independent presses will adapt quicker, and this will give them a chance to cut in front of the behemoths. Time will tell.
All this is not to say I'm opposed to self-publishing. For many authors, it is a brilliant way of getting their work out there. It is not just an easy path to take if you can't get traditionally published. From everyone I've spoken to, successfully self-pubbing and marketing your own book is a tremendous amount of work. If you can work hard, deal with the steep learning curve, and your writing is great, it is definitely possible to succeed.
It's just not the path for me. For the moment, at least. Who knows what the future will bring?