Certainly the Essential and Showcase volumes owe a debt to the manga format (it's hard to imagine Marvel and DC offering so many pages for so cheap without something to inspire them)
That something could be the Aussie reprint books, which have been around since the 40s, and were repackaging DC comics in cheap B&W albums till the 80s, sometimes with pages running to 300 plus. When I saw my first Essentials book, I recognised the Australian template.
I don't really think comics per se are in any danger, just Marvel and DC sales figures. (Here in Europe, comics are doing just fine, thanks, and indeed I shall be off to Paris in a couple of weeks to restock on some of our home-grown stuff.)
Exactly what my thoughts were when I said "cast your sights a bit wider".
And millions of adults read Manga.
Comics work best when they are true to themselves, because they do what they do better than any other medium.
They sure do.