顾问生病了，整年都在......我该怎么办？

I’m a first year grad student beginning this year. My professor was diagnosed with cancer and won’t be in, probably all year, maybe even the entire time I’m in class. He’s a great man, and also a nice man, which are two things that don’t always go together, so I’ve spent a while just being sad, but now I think it’s time to try to figure out what I’m going to do. I don’t want to make it to obvious who I’m talking about because I don’t know if he’s announced it publicly yet, but I am studying an ancient language… So he is the only professor in my program who knows how to read it. My question is do I change my topic of study to match a different professor at the school, or do I continue to focus on what I had hoped to focus on without the guidance of my advisor? Thanks so much for any thoughts you can give me on this topic.I’m a first year grad student beginning this ye