You could run a Redmere cable (they are uni-directional so pay attention to the orientation. The cables are marked) which is an active cable in that all of the electronics are in the sink end (tv side) and draw very little power from the HDMI input. The downside of Redmere is being as they have a chipset in one end, they could fail over time like any electronic device. However, if you're running them in a conduit, which sounds like you're doing, replacing the cable would be relatively easy because you could just pull a new one (as long as you don't have any harsh bends in the conduit). If it were me though, for a 50' run I'd use CAT-6 for that length and then HDBase-T. That's going to be a bit more expensive but the use of CAT-6/6a, at least for that connection, is about as future-proof as you're going to get.