My thoughts on the new Air...
Processor: Apple will probably be careful what they put into this new Air because of their product positioning, they'll want to clearly differentiate between the Air, 12" and Pro. For that reason, I can't see the Air having a Quad Core option, it'll be a low end 8th gen dual core, and probably in the same speed/GHz neighbourhood as the current Air, 1.6-1.8. I would be surprised if they even added an option to upgrade to an i7 this time. When they release the new Air, we'll probably also see the 12" receive the 8 gen upgrade otherwise it may hurt the 12" since it'll be the new MacBook that lag's behind.
Screen: The Retina they use will most likely NOT have P3 DCI Color, unless they also plan on upgrading the 12" to P3. Right now, the Pro having the P3 DCI display differentiates it from the MacBook 12", but once the Air get's upgrade, I think Apple will want to differentiate BOTH the 12" and Pro from the Air.
Keyboard: The new Air will most likely adopt the 3rd Gen Butterfly keyboard. The keyboard isn't something so awesome and unique that it IS the thing separating the Air from the Pro and 12", and Apple probably wants to make it standard across it's devices. Including the iMac's. Unless I'm wrong, I also don't think it's cheaper for them to maintain the current keyboard in the Air. Then again... Apple may keep the old keyboard in the Air to make the product positioning between the Air and the rest of the line clear, but I don't think it'll be for cost.
Ports: Magsafe is gone, and it'll be replaced with USB-C on the new Air, something Apple clearly wants to push and make standard throughout it's product lines, and now that other products are being updated this year. For this reason also, we probably won't see any other ports. Think about it logically... they won't add HDMI and USB-A just because people still want those. IF Apple listened to the demands of their Pro customer's, they would have stuck those 2 ports on the Pro notebooks already, so they certainly won't be added to the new Air. The Air is about Cost savings for both the consumer and Apple, so USB-C is my guess all we'll see on the new Air. Now how Many is another thing... no more then 2 for sure, but again, we may see the 12" upgraded with 2 ports if that happens, or in reverse the 12" will get 2, and the Air being value will only see 1.
Storage: 128GB default base IMO. Yes I know 128GB is weak in 2018, but for the market the Air is designed for; School/University, and those looking just to get into OSX, it's enough, and they'll probably add an option for 256GB max.
Everyone wants to see the Air updated with a fast 8th gen cpu, upgrade options like 512/1tb of storage, Retina screen, slim bezels, SD Card Reader, and same keyboard, but then what separates this from the Pro and 12"... Remember this is going to be a "Value" or "Educational" Mac, much like that old Education iMac back in the day.
Apple wouldn't upgrade this new Air to 8th Gen, Retina, same keyboard everyone loves, an SD Card slot, because it'll then most likely be used by many for Pro work... and they want you to buy their Pro line for that. This is a low cost, not overly powerful new "Air" and if you need faster and more power & options, the 12" and the Pro line await.
What the original Air laptop was is gone, and it's been replaced with the 12", and when more power is needed the 13" Pro awaits. The Air's target market will now be "Value" and "Educational" which is a bit surprising they are keeping the name apparently, and not changing it something like eMacbook, again like that old Education iMac back in the day.
Just my 2 cents. I could be all wrong