Bit of a sore issues with some of us mac enthusiasts; it was to allow 5k display with the limitations of TB1.2.
Skylake, TB1.3 may hopefully allow target display mode.
I think as many people who miss this feature should let Apple now that TDM is being dearly missed.
You can use the Thunderbolt port and a Capture Card to connect HDMI devices such as a Sky Box/Console. Check out the Avermedia ExtremeCap U3 - although it may be just worth purchasing a new TV considering the outlay.
I can't see the point in buying such a beautiful display and then worrying about why you can't display a low resolution image on it. If you only need HDMI / 1080 / TV quality just buy a cheap TV for peanuts.