I'm a video editor working on a PBS documentary right now, using a version of Avid from 2018. The software like this that I have to use for work will take a while to support Apple Silicon and newer OSes.
I will be curious about this. I expect that Avid will have
Media Composer and
ProTools running on Apple Silicon very quickly (as they are important to Apple and that will get them help). I would be shocked if we did not see Blackmagic Design's
DaVinci Resolve running on launch day and pretty close to that for Adobe's
Premiere/After Effects. However, I would guess that even if everything shipped at launch, you would not switch in the middle of a project, just as you probably lock versions during a project, right?
The day after the keynote I picked up a sweet deal on an 8-core Macbook Pro 15" 2019 with 32GB of RAM, the last model that supports Mojave (the latest reliable Mac OS.)
I misread this as you bought at 2015 MBP and I was thinking "WTF?".

The 32GB of RAM will be a big deal for you, I bet. My BF also edits, mostly using
DaVinci Resolve these days (although some
Premiere and Avid projects still) and he has found that the extra RAM on his new Mac Pro made a big difference.
This should last me for the next 3 years while everybody works out the kinks with this transition.
I expect this transition will be much faster/smoother, as Apple has been working on it since their first A-series processor. However, from my experience in production, most people lag releases anyway so I expect the same for hardware.
You never want to buy the first version of any major new Apple product anyway.
While people love to say this, it is not really true. It really depends on what the product is and how one needs to use it. The Apple Watch is a great example. People on both sides of the "no first gen" debate use it as an example and I think that is fitting.
I had been using an other fitness tracking watch from Basis Science (a company acquired by Intel for $100 million and then killed a year or two later issuing everyone full refunds on old products). I acquired a Series 0 Apple Watch and was very happy with it until I switched to my Series 3 (and then Series 4). While those who argue against first gen products say that it was too slow, the battery life was too short and it did not have GPS, those who bought it had a very functional product for a full year before a better version came out. The benefits I got from using it for that period greatly outweighed those detriments.
Given how long they have been working on their own designs and how important they think this transition is to them, I expect better results from their first gen Apple Silicon machines than other people on here do.