The thing with Puppy is that due to the way in which the majority of folks run it, updating is not a major concern.
For most Linux users, they're obsessed with keeping everything bang up to date. They're also as scared as hell of 'running as root'. But, when it comes to doing so, what are you afraid of really? Messing the system up, or losing your personal data? Here's what BarryK has to say about it:-
http://barryk.org/puppylinux/technical/root.htm
Because of the unique way in which Puppy works, you can run the LiveCD session without ever saving anything at all. Anything 'nasty' that may have gotten into your system during the session disappears into thin air at shut down.
Here's another 'take' on it:-
https://igurublog.wordpress.com/2010...fear-not-root/
If those older Pups still work for you, and do what you want, they'll continue to do so. Upgrading is purely a matter of personal taste. I run a kennel-full of Puppies, right from the newest XenialPup all the way back to Lucid and Racy (Wary on steroids, as it's known). They all have their own personalities, and they all have their particular uses for me.
A couple of our forum members are already developing Pups based on the most recent offering from Canonical; Artful Aardvark. Puppy development is very much alive and kicking. The most probable reason for the apparent non-development you've noticed is because round about the time that BarryK 'stepped down' from the helm, and handed over active Puppy development to the Woof-CE team, there was also a major re-shuffling of Puppy websites & domains. Puppylinux.org was the old, original 'home' site.....which has since been side-lined.
I've never yet heard of any Puppy user incurring major problems through running it.....because with the 'read-only' nature of the file-system (and its tiny footprint), replacing Pup is the work of a few moments (should it ever become necessary).
Mike.