Digital music.
Digital video.
Digital book.
With all the FUD about "ebook sales are dropping" they may be looking to rename the format to draw in casual readers and trailing edge adopters who might be scared off by the FUD. Also, as many suspect, to ease any confusion that you need a kindle to read the book.
One minor advantage of "digital book" vs generic "ebook" is the BPHs have stopped reporting total ebook sales value and have started lumping them in with a audiobooks as "digital". So, if the "big boys" want to phase out the term ebook in favor of digital, why not humor them?
It's not as if heavy readers will be confused by the change, right?
"A rose by any other name..."