According to 1Password's support forum, "1Password 6 supports 1Password.com accounts, and that will run on iOS 9 and 10"[1].
The iPad 3 was quite problematic as a device in that it was very RAM- and CPU-limited. With a 1GHz dual-core A9 and 1GB RAM, it was not going to handle future iOS updates well.
The next version, the 2012 iPad, runs iOS 10 and is still useful -- I still have one lying around for when I need an iPad (and I do have 1Password on it). And the 2013 iPad Air runs the latest iOS and I expect this to continue as iPad tech plateaus.
Lack of OS updates isn't unique to Android, but Android manufacturers collectively have a very blasé attitude to updates, much worse than Apple and Microsoft.
[1] https://discussions.agilebits.com/discussion/comment/408090/...