All 4K TVs can play videos from USB flash and HDDs. Few have SD card slot.

General categories of TV players

• Can play only moderate bitrate FullHD material encoder using H.264 (some Chinese sets and few others), top bitrate usually 50Mbps
• Can play FullHD and UHD H.264 with bitrate and fps restrictions, usually it is 30fps for both, 50Mbps top
• Can play FullHD and UHD H.264 and HEVC with bitrate and fps restrictions, can be up to 60fps for HEVC

Example of Samsung UHD player in best modern TVs

• Can play HEVC UHD up to 60fps, 50Mbps max
• Can play HEVC FullHD up to 30fps, 50Mbps max
• Can play H.264 UHD and FullHD up to 30fps, 50Mbps max

LG UHD TVs also have very similar restrictions.

Now you also can get idea why Samsung is used specific bitrate for NX1 camera :-)

And why you can not expect just get any raw content from your GH4 and show it to client in an instant.

4K / 60p

High speed display in 60 frames per second of 4K video (3,840 x 2,160 pixels – Ultra HD), which has four times the resolution of Full Hi-vision, for highly detailed videos with extremely smooth movement.

10-bit gradation

Previous Blu-ray Discs displayed the color signals (Y, Cb, Cr) in 8-bit gradation each (256 gradations). By expanding this to 10-bit gradation each (1,024 gradations), even minute signals can be faithfully reproduced to realize richly textured video.

High Dynamic Range

A technology that drastically expands the brightness peak from the previous 100 nit to 1,000-10,000 nit, marking a significant leap in the dynamic range of the picture. Bright light sources (e.g. lights or rays of the sun) and reflected light (from metal or water) that up to now were difficult to display can now be shown in rich textures.

BT.2020 wide color gamut

Compliant with the ITU-R BT.2020 wide color gamut signal formulated for 4K/8K broadcasting. Enables vividly rich coloration not previously possible on Blu-ray discs (BT.709 standard).

HEVC (H.265) / 100Mbps

Support for the highest 100Mbps video signal using the latest high-efficiency video compression technology. Compression efficiency and high bit rate far beyond previous Blu-ray discs (MPEG-4/AVC (H.264), maximum 40Mbps) enabling outstanding playback of high quality video with 4K/60p/10bit, High Dynamic Range, BT.2020, etc.

http://www.projectorreviews.com/home-theater-and-projectors-the-technical-side/ces-2015-whats-new-for-home-theaters/

4K content is almost absent for now.

What is available now?

• Netflix offers limited number of content
• Samsung offer HD with some UHD films, some of them no better than FullHD ones
• Sony 4K Ultra HD Media Player offer some content
• Most paid UHD films providers just use upscaling coupled with sharpness filter
• Lot of short demos (suitable to make wow, for visitors only)

How soon it will change?

No one knows for sure, may be year or two. May be much worse.

Situation still unclear with 4K Blu rays.

Overall

Overall situation looks much worse compared to 3D TVs.

TV upscalers are, of course, much worse than good software photo upscalers and you know that they can't do much, if anything at all.

It is still very early days.

What is the state of current 4K TV market?

HDMI. Around 90% of all owned TVs have only HDMI 1.4 and do not have support for HEVC playback. Read - they can play only up to 2160p30 in H.264, same 30Hz restrictions remain if you want to connect it to player or PC.

Market. Around 80% of models offered have same restrictions, only exceptions are new LG, Samsung and some Sony models. All largest Chinese low end offerings still have restrictions.

Future. Actual support for 10-bit, extended dynamic range and rec 2020 are absent. Some TVs can decode this videos and try to adjust to their usual panels.

OLED. OLED TVs are still present in premium sector and do not have 4K resolution in consumer market.

Marketing. Still focused on StupidTV features (in same horrible state mostly) and local dimming options in higher end sets. Almost all manufacturers do not make TVs with proper backlight focusing on thin edge lit models. Direct LED now is mostly territory of low end sets where very few leds are used.

As you can see, Panasonic supply some chips to LG.

Most important thing is to see is how far 4K TVs are from their cheap FullHD analogs (that are highly integrated, usually with just main LSI, Flash and RAM) and how big is cost reduction potential.

All images from http://www.realhd.co.kr/xe/general/23202

Newest 4K TVs support HEVC and HDMI 2.0, but they still come with usual DVB-S2 satellite tuners, same as all tuners that you can find on market.

New standard for 4K satellite transmission will require new hardware.
Whole point of new thing is to make modulation more complex and add more advanced recovery information.
In other words - satellite operators and owners want to get as much as they can from their old ill horse.
At your expense, of course.

As usual they claim unrealistic gains.
And tell fairy tales how they will transmit channels using high bitrates (never happens usually).

• http://www.newtec.eu/article/release/first-ever-uhdtv-4k-transmission-with-dvb-s2x
• http://www.digitaltveurope.net/241802/dvb-highlights-hevc-and-dvb-s2-developments/
• https://en.wikipedia.org/wiki/DVB-S2X