system
Given the following post, respond as if you're commenting on Reddit:
human
This one sucks. My research supervisor has taken medical leave and we aren't sure if he will make it back.

I adore him and I'm gutted that he's going through this. It's all been sudden, I know he would have done everything he could to make arrangements if he'd had any time to prepare. What I know for now is that he's taking time off to pursue treatment, and no one can really predict what will happen. So, I'm grieving and in shock, and I guess I have a few questions that you guys might be able to help with:

1) If there is anything we can do to support our supervisor. He is closer to some of us more than others (our lab is postdocs down to interns). He has always been open about things going on his life, but never really been vulnerable (or perhaps only on a rare occasion). We'd like to visit (in time) but don't know if that's appropriate. Sending an email back saying, "hope you get better, fingers crossed we see you next year!" seems so... lacking. 

2) On a more personal level: I am in the writing up part of my dissertation, and should have been completing within 6 months. I am meeting my school advisor next week, and I know policy is to usually hand off to secondary supervisor when needed. My secondary supervisor is be capable of seeing my degree through to completion, but I feel like all the intellectual work was with my primary, and feel awkward about transferring. Partly due to authorship concerns when we go to publish: my secondary has had no input into any of my work so far, and there are researchers from other universities who have been more involved (lending me their data, giving critique on experimental set up etc), and with whom I'd feel more comfortable eventually publishing with if required. At present, I am happy to continue writing without supervision and hope that my supervisor makes it through. I have collaborations that I can pursue in the meantime, and I could delay my degree for a bit if that would help. I'd like to propose this to my school when I meet next week, but I am wondering if there is anything else I need to consider, or reasons this is a terrible idea. 

Edit: I ramble, and have tried to edit down to be a bit more concise.
gpt
Can you also ask your department chair or committee members for advice?

You could send your advisor a card, flowers, or food. If he has family members involved in his caretaking, food may be especially useful for them as well. Something like a fruit basket, or something from Harry and David could be good. 

Please make sure to take care of yourself too. Your school likely offers free confidential counseling service that can help a lot.

Best wishes. *hugs* if you want them.