If Microsoft wants to compete with Apple and Google they need to provide a device that is much cheaper than $500 to interface with a TV, ChromeCast and Apple TV are sub $100 devices and that is what I'd like to develop against. If you step back and look at what Apple has with Apple TV all of their devices (desktop, laptop, tablet, and phone) can send the screen directly to it. In addition there are apps on the Apple TV for audio / video.
I get that Smart glass is trying to provide additional information about what is shown on the TV but there is a bigger market for the area that Apple TV and ChromeCast address, an area that Microsoft doesn't address at all because WiDi / Miracast basically has the PTV-3000 from Netgear and the only thing it does is stream your screen, there aren't any apps on it and it costs more than ChromeCast and is about the same cost as Apple TV.
As of Windows 8.1, we support Miracast to add wireless displays to your devices. Miracast is a standard supported by the Wi-Fi alliance. Newer televisions are coming out built in with the standard, but for now you can pick up an adapter much like the ones you list above well below the $100 mark.