1. Not counting the 2-port 13" MacBook Pro - which honestly was the true successor to the 2010-2017 MacBook Airs - The MacBook Air's last design refresh was in 2018 and has persisted across four releases. I would say it's much more likely that we'll see a design refresh of the MacBook Pros before we see it on the MacBook Airs. We're already set to see such a design refresh on the Pros next year with the launch of the Apple Silicon 16" MacBook Pro and whatever Apple Silicon Mac notebook replaces the current 2020 4-port Intel 13" MacBook Pro. That is, if rumors are to be believed. I'd expect the Air to be similarly redesigned a couple years thereafter.
2. Whatever M1's successor SoC, plus maybe a CTO option for a fan. Possibly RAM options beyond 16GB. I wouldn't bank on four Thunderbolt ports; though I could totally see three (the tapered design makes it difficult to fit more than two ports of any variety on that thing; they'd have to either reposition or remove the headphone jack to do four). Otherwise, I expect it to be externally similar to the 2020 MacBook Airs.