It's definitely possible and if so I think this is the year it'll bite them in the ass as iOS updates are starting to get almost as large as half the device storage needed to update.I really do think it's at least partially as simple as them being able to shave some additional costs off of their manufacturing by going with 16GB. They won't lose business by having that model as the entry point. They probably have reports from users who buy the 16GB because it's entry-level and relatively cheap. That, and the emphasis of cloud storage is quickly making the idea of large storage obsolete in its own little, weird way.
I remember I use to bloat my devices with music and TV shows so much that I needed the maximum size, but now I just use streaming music and video services, so 16GB in many ways reflects a situation where I don't need the excess room and I'm able to save some money.
I would say the majority of people who buy iPads just use it to browse the internet and watch stuff on it. There's a lot of productivity work and gaming, but most people with iPads I know just use it to stream various services, and 16GB in that regard, while not great or modern, is completely acceptable.
iOS 8 was what, 5.7GB or something like that. You need a little more than twice the space to install it (has to unpack it and be able to move files around). The only reasonable option for people who actually take pictures with their devices (my neophyte mother even does) is to install it via iTunes. I'd argue most people don't realize that now. 16GB really feels like 8GB a few years ago. It's my belief that it's just not enough for most people.