Actually, some bird species decided to stop flying (not really suddenly, but yet).
Since so many other humans before you have killed other humans senselessly, is it a duty for us to go on with it?
I don't think, you can derive any duty from the deeds of your ancestors. It's your choice, & this choice is largely based on your instincts.
I noticed that I didn't answer the original question "Is your offspring's future one of your life's purpose?" In my case: a definite no. Whether I procreate or not would be essentially a decision of my girlfriend/wife. I'm not really interested in having descendants. If I should have some, I'd care for them until they can look after themselves. That would be it. Their future is in their own hands.