That's a definite possibility. They no doubt wanted to save the announcement for the 20th Anniversary, so it's not surprising it was kept under wraps for so long if that is the case and they spent most of last year working on the translations. I'd like to think that Game Freak are that efficient, but...well, we'll see I suppose. That they only showed bare bones concept art and design makes me wonder just how far they are with it, as it implies they're not very far along at all, but then they'd have to work very quickly to get it out by year's end if they were only that far along, and that would lead to the question of what on earth they were doing all last year.
Hmph. I for one didn't appreciate the utterly unjustified and ridiculous extra week's wait. Sure, I've had worse, but there was absolutely no need for it, especially after XY were worldwide releases. Let's just hope they get their act together for these ones. I'd be willing to wait longer if it meant I got them at the same time as everyone else.