It all depends on exactly what you mean by saying "Wing Coaster". RCDB has confused things somewhat as they have a generic category (which includes 4th Dimension roller coasters, ZacSpins and Furious Baco) called "Wing Coaster" while also listing "Wing Coaster" as a B&M line.
This article I found on the internet explains it nice and quickly:
http://coasterpedia.net/wiki/Winged_roller_coaster
If you're going by RCDB's definition of a wing coaster, well there already is one in Japan. But I'm assuming you mean a B&M wing coaster. I suspect there will be a Wing Coaster in Japan at some point, but that's just a guess.