I wouldn't be worried about the audience itself "changing"... but that they will be so heavily exposed to Big Pub advertising and product, which will be right out front at every major books site, that they won't venture past it to find the indie content (not too different from what happens at major bookstores, in fact), and in time, may stop looking.
I also don't expect Big Pub to be interested in indies... they'll be too busy trying to crowd them out to sell their own products.
|