I've always seen the "Super Mario Bros." series (2D Games) and the "Super Mario" series (3D Games) to be brothers under the Mario family tree. Each brother has similar traits but is also unique from the other, but in the end I see each release as a new "real" Mario game. (For example, when NSMBWii released in late 2009 and SMG2 released in early 2010, I saw it as two Mario games releasing very close to one another... and I was very happy. )
So when the OP asks, "When will the next real Mario game release?" I'd answer, November 13th when Super Mario 3D Land releases. If he asked "when will the next 'Super Mario Bros.' game release?", then I'd have an entirely different answer for him (hopefully when the Wii U launches... I wanna see New Super Mario Bros. Mii!)