Yes, 4k blu-ray will require new players (disks can hold up to 100GB via three layers at 33GB per layer, and video is compressed using H.265 for additional efficiency). The PS4 may end up supporting it via firmware upgrade but nothing concrete yet.
Sat companies would need to provide H.265 capable set top boxes, existing sats could transmit H.265 signals.
The reason to go to 4k would be heavily influenced by your current TV size and viewing distance, if you are sitting a fair way away your eyes wont be able to resolve the additional detail. Makes most sense at projector sizes but the cheapest 4k projector starts at around $8000...
Bunch of older video cards can drive a 4k TV at 30Hz via HDMI 1.4 or Displayport to HDMI cables, which should be sufficient for video playback. For gaming 60Hz support via HDMI 2.0 would be preferable. What video card do you have now?
Once I get the Amazon refund might go for this 43" Visio 4k tv for desktop duties, $550 at Walmart:
http://www.walmart.com/ip/43310252