If your guy wants to know more about the future, Tara, he has the right to know as much as you. If you keep asking "if you were us" questions together at clinic, and reassuring staff that you prefer specificity, you will get an answer. It can be easier to say, is it reasonable to expect the current level of function...rather than asking about survival time, which some clinicians have antipathy toward.
That said, often P/CALS can answer the question themselves, at root. Progression is faster at the beginning and end, generally.
The five prognostic keys I see most often are nutrition, hydration, respiration, social interaction and ability to transfer, coupled, unsurprisingly, with positive expectations -- something to look forward to.
Best,
Laurie