Hi Eduardo, I fully believe that it is possible to manufacture a durable, weather proof articulated screen...for a price. While there are situations where this would be quite handy (many macro situations), for me personally, I know that for 95-98% of exposures it would be left flat.
For a pro-level body, having an articulating screen that would meet or exceed my standards of functionality and durability would likely result in an end-user retail cost of around $300-$500. I freely admit that I have high standards. I would expect to be able to *accidentally* hold onto the screen and hold 10+ lbs of body + lens. I am not suggesting I would go around doing this all the time, but boy would it suck to be left holding a screen while $10k of glass fell straight down (not too worried about the body, I know that would survive). Even with my limited use, I would still be interested in an articulating screen, even at the cost described above. But, I suspect I am in the minority with this view. For reference on how people feel about $500 price differentials, look at discussions on 5dMkIII vs D800. While I don't view the price difference as significant, especially as both cameras are amazing in their capabilities compared to where we were just a decade ago, I once again seem to be in the minority with this view.
Honestly, I would prefer the HDMI monitor solution to an articulating screen, even at a higher cost, as I feel it adds greater versatility (although more cables, batteries, etc are always annoying and make for more things to break).
All that being said, I feel that we are very near the pinnacle of achievement for 2D, still, planar capture device's practical capabilities. As the old battles are drawing to a close, the major small format digital camera manufacturers are heavily investing in new areas, such as video. 3D may be another area of growth. A long forgotten area that requires little research is usability. Clearly your suggestion fits into the arena of usability. Some players may choose to focus more on this area. Clearly the EVIL cameras (electronic viewfinder, mirror-less inter-changable lens) are attacking this market. So, it seems that Canon and Nikon are focusing on video; Lytro is interested in multi-planar/light field; some companies have 3D interests, though quite lame implementations at the moment; and others such as Sony, Olympus, etc, are focusing on usability.
Each time a company begins developing a new camera, they generally choose one of the technology tracks to focus on. Canon and Nikon's bread and butter has been resolution for quite a while. In the previous iterations, Nikon has done ISO (D3), resolution (D3x), ISO (D3s), resolution (D800). Yes, the D4 is resolution+ISO, and breaks this pattern slightly, but you get the point. The D4 is lower resolution than the D3x (but is higher than the D3s), and isn't mind-bogglingly better ISO than the D3s. The D4 is also a huge leap forward in video technology for Nikon. As they develop the D5, Nikon will have to evaluate what will best position them in the market. It seems less likely that ISO or resolution will be a major area of technology research for this product. Video technology, while time consuming to develop and perfect, is largely software. Only time will tell, but I suspect usability will play a larger role. But advertising ergonomics and usability is quite a bit more difficult than being able to simply say "50% more pixels" "100% higher ISO" (lol, 1 stop, but it sounds so good).