Journeyed there and back again
Publishers may be losing income, but they're still the first place most talented writers look to publish their work.
The biggest sales fall of any demograph of writers has been trad debut writers. It is astounding how much their income has fallen - and these are career ruining falls (because low debut sales impact on every future release) Frankly many writers take one look at the fate of many trad debuts (low sales, dropped on the back of it) and decide to build a different way.
Many dedicated self publishers aren't doing it because they can't get a publisher - but because they don't feel getting a publisher is important in the current climate.
The incentives for writers themselves, particularly the genre-redefining authors of quality comparable to Martin, Jordan, and Abercrombie, seem to have grown larger. Audiobooks, ebooks, and film seem to be on the rise for the genre.
Plus - the authors you name are all well established and predate the shifts in the market we've seen in the past few years.
Top authors are signing 7 figure deals for upcoming books, shows, films, etc.
I think that incentives for authors are a better predictor of genre growth trends than publisher profits. Most of the best of those authors will still publish through traditional publishers. Those publishers aren't too likely to let the next Martin or Jordan slip through their fingers.
Sorry. I know this might burst bubbles but for the vast, vast majority of authors a traditional debut, with no previous record or following, is a career risk. Which is why so many of us are coming through in other ways - and why the breakthrough trad authors are few and far between.
And the losers are the readers with less new quality material coming out (all but the biggest authors have day jobs so produce less) and much of it emerging through channels that are harder for the reader to find them in.