Apple will most certainly not drop 16GB. As some others have mentioned before, Apple's biggest profit comes from the 16GB model, as it is their base model.
And as you may have figured, the reason why Apple didn't loose the 16GB and bumped the stock option to 32GB, is to whereas Apple wants you to buy the higher priced 64GB model.
I wish Apple would decrease it's bezels. Most preferably for the Plus, but while they are at it, why not the normal '6s', too?
Probably won't happen as Apple keeps the design of the 4 and the 4s, the 5 and the 5s the same, so the 6s will most likely look alike the 6.
And I wish Apple would use the rendered resolution on the Plus. That'd be 2208 x 1242. Now it is rendering at that and down-scaling to 1080p.
What I want the most is to combine the decreasing bezels, with the 2208 x 1242 pixels in a 6,0" screen format. I don't find the 6 Plus too big, I just want the bezels to be smaller so I'd have more screen estate.
If they do that, they'll end up with a PPI of approximately 422.
It would probably boast the A9 chip, along with the M9 (but heck I know what they could improve on that..). It will most likely sport the tri-cores found from the A8X, but probably at a lower production process and maybe down-clocked a little (for power consumption).
As seen on the iPad Air 2, the 6s will almost certainly boast 2GB of RAM. I haven't had a Air 2 in my hands yet but I have had an Air 1. But the difference in responsiveness and whatnot will be (alot, I pressume) better.
Maybe they'll do this year something about the speaker set-up. The mono speaker on the iPhone 6 is no slouch, but it is mono... really?!
So I suspect stereo speakers.
The earpiece speaker becomes a loudspeaker, and would like to see the ring around TouchID disappear and let it become a ring speaker.
Maybe they can keep the bottom speaker like the current 6, to boast volume or for the extra punch.
They might add wireless charging out of the box, along with a docking station where you can lay it on.
I suspect they will finally change the camera sensor to the Sony IMX240. Meaning 16 MP or the IMX135 meaning 13 MP.
As for the front camera, I think they are going to use a camera similar found on the iPhone 4 with it's 5 MP with updated internals to match that of 2015.
They might include new Beats earphones in the box, however I find that highly unlikely. Apple is currently rocking those stock earphones for a long time for actually almost no additional cost. They'd shoot their selves in their foot if bundling Beats earphones, because they can and will make a huge profit out of those.