I ran into this issue a few weeks ago… The option for “Connect to a wireless display” was no longer available on my Surface Pro 3. It disappeared on my Acer S7 laptop, too. What the heck is going on?!?! Well, I figured it out with some sleuthing on the interwebs… Oracle’s VirtualBox, for whatever reason unbeknownst to me, disables support for WiDi and Miracast in Windows 8. Uninstalling VirtualBox solved the problem. I also read some VPN clients cause this issue to occur, but that didn’t appear to be my case.
I’ve logged a bug with Oracle – this is a usability bug and should be fixed. I’d love an explanation as to why it’s disabled.
Here’s the bug: https://www.virtualbox.org/ticket/13998
I hope that helps anyone having a similar issue!