I actually would bet on the screen getting updated for the Pencil before the other two.
The speakers require space, and in the Pro serve to also keep the iPad lighter. Apple could have put more batteries in, but at the expense of making it even heavier. But the speakers don't add nearly as much weight. To bring them to the Air would require carving out space the battery and logic board currently need. It isn't impossible, but I don't feel like there is a rush to re-engineer things to do it. At the very least they'd need to bring over the variable frame rate timing from the Pro as well to avoid losing too much battery life. I'd rather see them bring it to get an extra hour or two from the existing battery. Plus, if you want force touch, that also needs space for haptics.
The smart connector isn't an accessory heaven, and it's basically going to only be good for keyboards and maybe some form of power dock. It doesn't have the data rate to do anything useful in this day and age when USB2 is old news, and it makes USB2 seem really fast. I don't mind if it doesn't come, because keyboards will be somewhat cramped. I'd rather have a nice stand or Smart Cover and a wireless keyboard that is more full sized.
But if it gains Pencil support? Day one buy for me. I already gave Apple feedback saying that.