I want to casual shooting (family, travels etc.), but I do not want to sacrifice the quality.
Should I buy a camera equipped with 4K shooting? Is it the right time to buy a 4K camera or should I buy a 1080p now and may be after 2-3 years I will buy 4K.
From my perspective, 4K is still not evolved, it will take another 3-4 years to reach its peak and that's when I think more and more cameras will be available with affordable price.
You will pay substantially more for a good 4k camera right now than you would for a good 1080p camera. Quality =/= resolution, there are phones that can shoot in 4k but the videos will look a lot worse than a 1080p video from a dedicated 1080p camcorder/dslr, the image quality depends on a lot of factors. A bigger sensor for example has the ability to capture a lot more light and have much more accurate colors than a tiny sensor that only captures very few photons per pixel. The video compression used by the camera is also a big factor, even with h264 there can be huge quality differences between cameras depending on the encoding settings of the camera.
The question you should also ask yourself, what do you get from a 4k resolution when you mostly shoot things that are meant to be memories that you don't already get with 1080p.
My advise would be to not think about 4k and look for a nice 1080p camera. Even in commercial video there is not that much to gain with 4k video right now and probably not even in the future, we are reaching resolutions that don't necessarily improve the image quality for every content. It really depends on what you shoot and most importantly how big your screen is and how far you sit away from it. Right now there are quite a few living room configurations where its already hard for a lot of people to tell the difference between 1080p and 720p.
I agree with your assessment that 4K isn't ready (or affordable) yet. Consider what you want to shoot, and what you're willing to carry around to do so. Then find a 1080P camera within your budget.
As already stated, the total resolution isn't as important as the sensor size/quality, lens quality, in-camera compression (the less the better), and stability/ease of use.
A benefit of 4K: you can zoom & crop a 4K wide shot to give you a close-up if you plan to output 1080p. Nice for commercial productions still outputting 1080p (capture establishing shot & zoomed shots simultaneously & blow things up w/o loss of quality)... But for family vacation movies & stuff it wouldn't serve much of a purpose unless you plan to edit the footage extensively.
Also as alluded to in an earlier comment - what are you watching the video on? There are very few 4K screens out there at the moment. You'd have to edit & reduce the resolution anyway in order to view it ... Or also buy a 4K TV and computer monitor in addition to the 4K camera. For that, you could buy a nice 1080p camera plus your kid's 1st semester of college :)
Finally, capturing all the footage now & saving it until 4K is more widespread means having to store really large raw video files you can't watch at full-res in the meantime anyway. You'd also need to purchase more external hard drives, more memory cards, and probably a Blu-Ray burner with discs for backup. 3-4yrs from now that might not even be compatible technology.
I'd argue that for casual shooting (family, travels etc) you are not going to carry an expensive bulky camera, you are likely not going to carry anything on you… except maybe your mobile phone. So I would look into buying a cheap mobile 4k device. Two good looking recent mobile phones able to record 4k are the Samsung Galaxy Alpha and the Sony Xperia Z3. You can see a comparison video of both but due to youtube recompression I would recommend downloading the raw 4k footage from mediafire.
Compared to 1080p mobile cameras both of these 4k videos are great. But they are still far away from a good 1080p camera with nice optics. Still, for around 500$-700$ you get to experiment with a new resolution. It also allows you to prepare for a 4k video edition workflow. For instance, if you thought about using Apple's iMovie to edit the footage forget it, it's not supported. And you will need about four times the space to store and four times the time to edit/compress. It can be a good test to play with these mobile videos, maybe you find out that the real bottleneck is at your desktop in postproduction!
With regards to quality I'm sold on 4k. Youtube looks horrible on any resolution, but I've watched a few videos from cameramen posting torrents of their recordings and they are awesome. Unfortunately I agree with Professor Sparkles: for mass media 4k is still a long way. Heck, I still watch from time to time poorly compressed 1080p tv which looks worse than a DVD. And don't get me started on TV programs upscaling low resolution youtube videos… ugh, my eyes.
I would recommend waiting at least a few years. 4K technology isn't very integrated into technology yet. Most people can't enjoy 4K quality unless they have a several thousand dollar screen. 4K cameras are still very expensive compared to 1080p cameras. Wait for the technology to become more common and the price of 4K cameras will drop.
