The only 4K TVs which have DisplayPort are from Panasonic. DisplayPort is not essential, every 4K TV has HDMI 2.0 connectivity and this can be utilized with the GTX970/980 cards, currently the only ones which have the HDMI 2.0 output. For playing games at 4K those cards are rather needed, even dual SLI is not excessive.
There are piles of HDMI 2.0 issues to consider when looking at using a TV for a computer monitor:
From cnet P series review:
"Like most 4K sets, the Vizio P series can't accept 4:4:4 chroma subsampling signals via any of its inputs. The company claims that's because three of the ports are compatible with HDCP 2.2, which doesn't allow 4:4:4 signals. This isn't a big deal to us since, once again, the only common 4:4:4 sources come from PCs."
From a credible source on AVS forum:
http://www.avsforum.com/forum/166-l...hroma-subsampling-thread-14.html#post29064553
Apparently the SiL9679 chip being used by TV manufacturers for HDCP 2.2 support over HDMI 2.0, the only such chip available currently, is only capable of up to 4:2:0 chroma at 4K at 60 hz. Anyone looking for full RGB color at 4K60 on a TV should try to find one without HDCP 2.2 and hopefully using another chip, if this is the case.
I don't believe that HDCP cares about 4:4:4 vs. 4:2:0. However the limited bandwidth implementations of HDMI 2.0 simply cannot support the data rates necessary for 4K video using 4:4:4 except at 24Hz and 30Hz. Silicon Image (SI) has just started shipping their new Sil 9777 full bandwidth (i.e., 18 Gbps) HDMI 2.0 chip with HDCP 2.2. This should be able to support 4:4:4 for 4K@60, but even then only as long as the bit-depth is only 8-bits per color. At higher bit depths you will be limited to 4:2:2 (at 12-bit depth) or 4:2:0 (at 16-bit depth).