It would be up to everyone else in the world. I'd leave the rights either with my partner or put them in the public domain, and if people wanted more content of my IP, they'd be the ones who would make it.
I make my work for other people to enjoy, not as some monument to myself. If I die and it's unfinished, there's no need to complete it unless people are all clamouring for closure, in which case, my partner would be able to access my notes and do whatever's best with them, perhaps release them online, or find an appropriate creator to commission.
The readers are the ones who decide if my work is meaningful to them and should be preserved and continued after I'm gone, not me. I wouldn't saddle my loved ones with the burden of trying to make people care about an unfinished work nobody was all that interested in just because I'm gone, so it would be their choice to make.