I think I'd prefer a Generations style expansion that added more for every lifestage. Something that made each stage feel unique and meaningful, with lots of milestone moments like going to prom, getting your first car or having a mid-life crisis.
I think a lot of features need a polish-up and a Gen pack would be a great time to do it. Retirement could do with some work. As could weddings. And it would be a good time to handle death in a sympathetic way, adding features like funerals and maybe a more effective period of mourning.
So yeah... I think I'd like to get more elder focused features in an expansion pack like that rather than a specific elder pack. I think a stuff pack wouldn't go into enough depth and I don't think an elder gamepack would have a wide enough appeal to the general community.