I think radiation oncology is going to be displaced by emerging disciplines in medicine. I would pay close attention to what is happening in the field of immunotherapy since there are a lot of recent success in difficult cancers, autoimmune diseases, and infections. Recently several specialists have supported immunotherapy's potential in cancer treatment (http://www.nature.com/nature/outlook/cancer-immunotherapy/). Unfortunately, training in radiation oncology will most likely be different than the training required to perform this type of medicine. Likewise, the potential for automation/technology/AI in this particular field is quite limited.

It's important to think about why medicine might be moving away from radiological therapies. They are poorly tolerated by patients and expensive (http://www.cancer.gov/cancertopics/coping/radiation-therapy-...). It's difficult to say what will happen in the next couple of years, but radiology in general is taking a hit since hospitals are trying to limit the use of expensive and unnecessary imaging often at the expense of radiology professionals (http://www.auntminnie.com/index.aspx?sec=ser&sub=def&pag=dis...). Choosing a career path in medicine should be more about how you like interacting with patients.