The main thing different about an M1 Air (compared to an Intel Air), which might cause usage of iPad to drop, is the ability to run iOS apps on the M1 Air.....interesting that no one who has stopped using their iPad has mentioned this!
Meh, I don’t know - maybe that will be true one day, but I’m not sure how true it is today... it certainly is not true for me, that’s certain.
And the reason is simple - the vast majority of iOS/iPadOS apps are massively inferior to their MacOS equivalents. Now, there are some thing the iPad is better for, but those apps are not relevant to the Mac, because the Mac doesn’t have a touch interface, so f.ex. drawing apps on iOS/iPadOS are mostly irrelevant.
Now there may be some iOS/iPadOS apps that don’t have an equivalent on MacOS, but I can’t think of may off the top of my head, that I’d want on my MBP.
In fact, I’d posit the opposite. iPad will GAIN use if the iOS/iPadOS quality improves to at least equivalence vs their MacOS counterparts. For example, I use a lot of word-processing software, including specialized ones (screenplay writing software), and I am always extremely frustrated by how inferior they are on iPadOS (compare Final Draft on MacOS vs iPadOS - ugh!). Now, if these apps become as good on the iPad as they are on my Mac, I can easily see how I’d use the iPad a lot more. As an example, I forced myself to use FD on my iPad for over a year, and it was always a chore compared to working in FD on my iMac. But the iPad was portable. However, since I’ve gotten the M1 MBP, I use FD there and the FD usage on the iPad has fallen off dramatically (except on those occasions when I take the iPad to places where I have to wait, like doctor’s waiting room etc. and it’s more convenient than lugging the MBP around.
Bottom line, to MY use scenarios, not being able to load iPadOS apps onto my Mac is not a factor - what would definitely make me use the iPad more is if I could load MacOS apps onto the iPad! YMMV.