I see nothing wrong with keeping pets that can and will outlive you.
Who's to say I won't get hit by a bus tomorrow? Does that mean I shouldn't have had my dogs, cat, geckos, and snake since they're now 'orphans'? Even the crickets I bought last week will have outlived me, was I unfair to them?
If you check around in (I believe it's) Portugal, you'll find a lot of Galapagos Giant Tortoises kept as pets. They've been in the family for generations. When the current owner dies, the tortoises are 'inherited' by someone, usually a trusted family member. The story in the news last week about Timmy, a turtle who died at the age of 160 in England is a good example too. He was cared for by family members, became part of the family too.
The thing to do is plan in advance. Make sure you have someone who will either take over the care of the animal(s) or can be relied on to find a caring home for them. Some people make specific reference in their will about the care of their surviving pets.