Seems like China Mobile has already confirmed (via 163) that the rumoured iPhone 7C will be coming to markets, atleast in China, in April 2016 and will cost 3200 chinese yuan (about $500). This information comes from the roadmap of its upcoming releases which China Mobile showed in the even held few days ago.
In terms of specs, there is nothing solid yet. It is expected to be coming with a 4-inches display having a resolution of 1136 × 640 and protected by a 2.5D glass, like the curved one you have seen on iphone 6 and 6S. It should be equipped with Apple’s A9 processor and 2GB of RAM. Also expect it to be coming with Touch ID and may be a metallic unibody design also.
Update I should have written iPhone 6C instead of iPhone 7C as pointed out by AppleInsider. Since the iPhone 7 lineup is still 8-10 months far away, we will rather get an iPhone 6C.