Back in the mid to late 2000s, HD cameras became affordable enough for the prosumer and indie market. That same trend is beginning for 4k.
There has been a number of really exciting 4k product announcements in the film/video industry.
Cameras
Sony recently announced 2 new 4k cameras, F5 $19,400 & F55 $34,500.
Sony already has a high end 4k camera, F65 for $65,000. The FS900, $9,900, which will be upgradable to 4k in the future.
Red, which created this 4k party, announced price drops:
RED EPIC-M: $24,000
RED EPIC-X: $19,000
RED SCARLET-X: $7,950
RED ONE MX: $4,000 limited supply of battle-tested bodies and is sold out.
GoPro released Hero 3 version of their compact camera, low cost camera. Hero 3: Black Edition records 4k at 15fps, $399. It also shoots at 2.7k at 24 and 30 fps.
In addition there is Canon 4k cameras: EOS-1D C $15,000 and C-500 $30,000, JVC GY-HMQ10 $5,000
I'd also like to mention the Black Magic Cinema Camera $3,000. It's not 4k, but at 2.5k and at a price point a lot of indie filmmakers find appealing.
Delivery
Sony as well as other tv manufacturers have 4k TVs available soon. Sony even has a 4k upscaling Blu-Ray player.
http://blog.sony.com/sony-4k-content
Sony announced the 4k Ultra HD Video Player, which will be loaned to anyone buying the Sony XBR-84X900 4k LED TV. It's essentially a hard drive based server with movies on it.
Red has announced their Red Ray 4k playback system for $1500.
What's it mean?
Do you give up your HD camera right now? Not yet. Broadcast in the US is still HD. It took years to get HD and I don't see it going to 4k anytime soon. So there isn't an immediate need to transition to 4k like there was to HD from SD.
What it does mean is you need to be more mindful of your options.
Think about how you want to distribute your project. Theatrical, broadcast, home video, online? Or maybe specialized outlets like digital signage and second screen.
What is your workflow? Shooting in 4k may be cheap, but not everything else will be. Storage requirements more than quadruple. You'll need more computing power to deal with the render times.
Is this a project that has a quick turnaround? Besides money, the other expenses are resources and time. Will you be able to finish your project on time. Even if you don't have a deadline for your project, you don't want to be stuck in post production limbo. VFX work is already time consuming, but at 4k will get exponentially longer.
These issues will become less of a problem as time goes on. Just as everything was transitioning from SD to HD, these same questions were being asked. Soon enough technology caught up with the needs, as they will again for 4k. Just be aware of all the pitfalls and realize not every project needs 4k.