I don't think a promise is dangerous, necessarily, but I would take it for what it is--an intention based on current circumstances.

When I started with my current therapist, I had lost a whole support team that fell to the side one by one, for various reasons (mostly moving and death). She pumped an arm muscle when I pointed out that she was the only one left standing. I took it to be a sign of endurance. That's really the most I (or you) can ask for--are they up for it and, barring any catastrophes, are they in it for the long haul?

I'm really sorry you're going through this. It's a loss unlike any other.