I personally think in this space that they experiencing more competition from boards with the ESP8266. You could use the rpi with the gpio pins but for some projects it doesn't make economically sense.
For 4 euro's and less you can buy a board with the ESP8266 and you can even use the Arduino IDE to program it.
Buy them on Aliexpress and they are even cheaper. You can now buy a ESP-12E for about $1.60 on Aliexpress. That's just the module though. If you want a breakout and a USB port they cost $3-4.
And yes, I think the squabble left people a bit unsure about Arduino and then they discovered that there's ... the confusing mess that is mBed :-)
It's not that he ESP8266 is fully a replacement and there are still lots of situations where you would lean towards the Atmel chips in the Arduino or others like PIC and STM. E.g. the ESP8266 is pretty limited on IO, not as tolerant of higher voltages, more heat/power, worse for sensitive real-time applications, inferior low-power performance and so on.
But for a lot uses they are a better fit. The ESP8266 is a right time and right place kind of thing - it has enough IO and wifi to be really useful for the hobby explosion of IoT stuff.
For 4 euro's and less you can buy a board with the ESP8266 and you can even use the Arduino IDE to program it.