I think the profile of the nRF51 is about to take a big leap forward, as the previous closed hardware design for the BBC Micro-bit, which has been rolled out around a million school children in the UK, has not been released on GitHub https://github.com/microbit-foundation/microbit-reference-design
There is a press release http://www.bbc.com/news/technology-37682405 indicating that the micro bit foundation will be encouraging the use of the design throughout the world.
I am not a lawyer, but the license appears to allow anyone to use these designs.
So if this is correct, I imagine that a lot of Chinese manufacturers would be interested in producing versions of this, because at the moment, they are only available in the UK and the cost is fairly high (£13)
Which would be good news if the price was brought down in line with boards like the Arduino Uno, or my favourite STM32 boards.
Update. May 2017
These reference designs appear to be for a binary compatible nRF51 board not the actual BBC Microbit board as given to students in the UK.
The board is much bigger and uses an nRF51 module rather than the nRF51822 MCU