...This isn't a scanlation-ish question, so I'm sure I can answer this.
Anyway... I haven't found any confirmation page on the Viz Media site but apparently, as stated on multiple anime/manga blogs, Reborn has either been dropped or put on hiatus. Viz has recently suffered from no sales and had to give layoffs to a lot of people, they even had to cancel Gimtama's USA releases due to no funds from fans.
Here's a link stating other manga titles that were either dropped or placed on hiatus by Viz, but as I stated before, Viz hasn't confirmed these claims: http://www.serebiiforums.com/archive/index.php/t-509952.html I'll keep lurking for a more trustworthy link.
I wouldn't be very surprised if it was placed on hiatus, knowing the state of the anime/manga industry, this will unfortunately happen to more titles in the future.
