As someone who has been incredibly excited for the Surface Neo, I'm really bummed to hear that it won't be coming this year. I'm intrigued at the idea of Windows 10X on single-screen devices, but I think the dual-screen aspect is the "carrot" so to speak to get developers to build modern Windows apps. I feel like 10X on single-screen devices is nothing more than an evolution of Windows 10 in S Mode, which didn't provide enough of an incentive for developers to modernize their applications.
Hopefully Microsoft releases a small batch of developer-focused Neo's for developers that want to get a head start building for dual-screen devices.