This comes from Justin Bieber's official Instagram feed, tweeted along with the hashtag #robin??
It is almost-certainly bullshit (the prevailing theory is he's promoting a Funny Or Die sketch), and the giveaway is the script itself: At this stage there very likely isn't a full script, if there was it wouldn't be out in the wild with a full-detail cover page using the actual title, the logos both look "off," etc.
That said... I wouldn't be at all upset about this. I'm too old to like (or even understand the appeal of, truth be told) the kid's music... but I also too old to be personally affronted by it or by his existence. Yes guys; nonthreatening, vaugely-effeminate boys who can sing are popular with teenage girls. That's not a new thing. Get over it.
To be honest, I would be "for" this strictly on the sole and sufficient basis that it would indicate a massive tonal and target-demo shift away from both "Man of Steel" and "Dark Knight," and also because it would make horrible, horrible Batfans' heads explode, and that's a great service indeed. I love me some Batman, folks, but at some point his fandom morphed into probably the most vile and awful of geek subcultures (and I'm NOT the only guy who noticed this) and at this point I'm inclined to support anything they'd hate on general principle. Remember, these are people who are petitioning the White House to prevent Batman from being played by an actor who is guilty of having been photographed smiling and appearing in comedies.
But, whatever. It is VERY unlikely to be real. What IS likely (plausible, at least) is that it's a brilliantly coordinated stunt. There's a vocal contingent of Batfandom that hates Robin on principle (they're the same guys raging about Ben Affleck, mostly), and this little bit of Bieber self-promotion could serve as way of inoculating them: The genius of Justin Bieber's career is that he embodies the sliver of overlap between "irrational-cannot-shut-up-about-it-LOVE" and "irrational-cannot-shut-up-about-it-HATE" in teenybopper pop-music, and if Warner Bros. was to announce a Robin in the near future whoever it was would no longer be the worst possible choice. Everybody wins.
Honestly? Since it's become pretty clear that WB isn't looking at their shared-universe DC movies to be source-material mash-notes a'la Marvel's crop up to this point, it might be a more interesting idea to let supporting-players like Robin be opportunities to experiment with unconventional casting, a'la "Man of Steel's" Jenny Olsen (who probably would've been more controversial if that film had given two shits about anybody in Metropolis.) A female Robin (Carrie Kelly, Stephanie Brown, somebody new, etc) would be quite the attention getter, especially since non comic-reading people likely have no idea that there have been female Robins. Plus, it would remind embittered manchildren of the "The Dark Knight Returns" - the Living Gospel of the Grim n' Gritty era, so there's also that.