I just finished watching the
latest Dragontalk podcast, and read over more of Mearls tweets . . . .
Looks like this particular product, the Wayfarer's Guide, will be updated as the UA playtests tweak various elements, and will eventually receive POD (print-on-demand) options, possibly including a hardcover POD. However, this specific product will not "become a real boy" and get a more traditional print release . . . . but material in it MIGHT be incorporated in a future Eberron traditional hardcover. This potential future book will overlap strongly with the Wayfarer's Guide, but will be a different product. The discussion so far is short on details and doesn't offer promises or release dates. And, of course, plans can change between now and a possible future Eberron book, especially with the experimental and playtest nature of the Wayfarer's Guide.
We'll see what happens, but if someday in the not-so-distant future we have two, overlapping and similar products, the Wayfarer's Guide and future-Eberron book . . . . that would irritate me.