You don't need to learn a specific RTOS there is zillions of embedded RTOS they segmented to markets niches and even if you know the exact segment you are going work on there is still a lot of OS's operating in same segment.
The important thing is to understand a basic concepts of operating systems, and have a strong C background.
When we are recruiting (we are embedded development house) we do not require any specific knowledge in embedded programming or specific OS. We are looking for smart ppl that write perfect C code and capable to learn.
