To start with Arduino, a blinking led is very exiting.
The Atmel chips like the ATmega328 are perfect for a simple job, but the cheap ARM chips are hard to ignore.
I think that a basic and cheap chips will be used, and chips with more and other possibilities will be added. So in my opinion, Arduino will be with us for the next 10 or 20 or 30 years.
The FPGA chips are something else, it would need a lot of work to get those into the Arduino IDE.
In the future a FPGA might be build into a microcontroller, to have the best of both worlds.