It's tough to get sad about things that will happen so far in the future. As for our sun expanding, if we as a species can't find another home by then, we deserve to go. As for the eventual heat death of the Universe, it very well may end like that. There are a few competing scenarios. Regardless, will a Universe, if not this one, start anew somehow? Will there really be a total end? We are pretty sure there will be for us personally, so it may very well be the same for the Universe. Interesting to think on, but nothing we need worry about. We do have more immediate concerns, though. Be nice if we took care of some of them or we may not have to worry about any of these others at all!