While we here in North America get a larger, Ninja 300, the rest of the world gets an updated 2013 Kawasaki Ninja 250; the smaller capacity better meets various tiered-license and insurance dealies elsewhere. Those other markets are traditionally more favorable to naked bikes too, especially the congested city streets of Europe and Asia. So removing the fairings from the new 250, fitting flat bars and aggressive styling that apes the Z800 seems to makes sense. That's what Thailand's TMC Blog claims anyways, saying this is an official sketch of an upcoming new model.
Looking at the sketch next to this side-on photo of the new Ninja 250 and you can see that the swingarm pivot plates match up, as do the tank, engine, swingarm, wheels, brake calipers and tail unit. The exhaust on the naked bike appears to be more heavily stylized, as is the item on the Z800 and Z1000.
It's unlikely that we'd see such a model in the US. Here, nakeds don't have a history of strong sales and even the marginal added cost of developing and producing a specific 300cc model for a single market would likely prove too high.