I think people who read the books and watched the TV show would still buy the last two editions of the book series. I know I would. As you said they are sort of different entities.

I found a couple of the differences between the book and the TV show made the TV show actually more dynamic for TV while his narrative in the books made sense from a writing standpoint. For example: in the book, the Hound and Brienne never meet and fight, but do so in Season 4 episode 10. Also, Arya was never Tywin's cupbearer in the books, but having a Stark right under his nose in the TV show also was more engrossing.

Martin is getting his well-deserved wealth. I have suspected he actually has the last two books already done - or at least mostly done - and is pausing their release to milk some well deserved income from video games, spin-offs and other Westeros related novels and books.