Advisor ill, out all year... how should I proceed?
Your best option, in my opinion, is to discuss it with him. You may need to wait a bit until he feels well enough to think about it, but you really need his advice about how to proceed. He may be able to help you in your current studies, or not. Depending on the illness he may also never return to work. But, if you need to change professors and projects, he can probably help you get started with someone else, and is probably the best person to do that. 

If you stay with the current project you will need to prepare for the eventuality that you will have to finish on your own. If that is the outcome, you will need to find resources to make that possible. It might be possible for you to continue yourself or not, depending on many things. But the professor will likely have advice on all of that.

I would advise against just making a decision without such advice. It may be that other professors in your department can give you the best advice about how and when to contact him. Good luck to you both.