x.x.1 updates don't normally happen outside of initial x.0.x releases and final builds of that version of iOS. Example of iOS 8 there was no 8.1.1, 8.2.1, 8.3.1. 8.4 got a 8.4.1 because 8.4 was the final version of iOS 8.
Well, there is and there isn't.
9.2 (or any non x.1.x release) usually include additional FEATURES or more defined enhancements to either base or new functionality or to address some serious deficiencies in functionality or features but not necessarily bad bug fixes.
These releases are generally reserved just for the actual developer community and not for the public beta community. (we only have a few examples so that doesn't necessarily a trend make)
We would probably get a 9.1.1. public beta, but my bet is that we wouldn't see a 9.2 PUBLIC beta.
There WILL be a public beta for 9.2. You're crazy to think there wouldn't. The Public Beta Program started with 8.3 and has had a public beta builds since (minus 8.4.1) Since the launch of the Public Beta Program there has been 8.3, 8.4, 9.0 and 9.1. It's not a "just a trend" when since the introduction of the program there has been public betas along side developer previews. (In many cases even same day releases for builds)
OS X has been the exact same since the Public Beta Program started summer 2014 with Yosemite. That got 10.10, 10.10.1, 10.10.2, 10.10.3, 10.10.4, 10.10.5, 10.11, 10.11.1