Heh, the exact reason I bought the book was to help show support for the product in the long run. I figured if they got money for the playtest material, the real deal was sure to follow, and have a much more broad-sweeping budget than they may have initially planned. Did the investment paid off individually, that is an overwhelming no - I barely used it. The 3.5 books, of which I owned everything Eberron, were just too easy to translate to 5e myself. Hopefully it will pay off overall, however.
And its for exactly this reason that no one who actually has played Eberron before really needs to buy the upcoming hardcover Eberron book. Nor why anyone really needed to buy the Wayfinder's Guide. Or needed to buy the 4E Eberron Player's Guide or the 4E Eberron Campaign Guide. Or the 4E Adventurer's Guide To Eberron or the 3E Player's Guide To Eberron. All of them have and will be repetitive re-written duplication of the same stuff we all received in the original 3E Eberron Campaign Setting other than a few game mechanics. Game mechanics that we've already received for free several times over.
Hopefully we've all been paying attention these last 10 years and have noticed this. And made our purchasing decisions accordingly. LOL.