Ah interesting. I haven't watched WWDC yet, but 2021 seems oddly early for the 16". Are you suggesting late 2021 earliest?
They said in the presentation they have a "family" of Apple SoCs. I don't think it'll be that long of a wait for an ARM 16". They've been working on all this for years already. If anything, the wait will just be due to the usual release schedule Apple tends to do, and not because the higher powered chips aren't ready. I don't know for sure obviously, but that's the vibe i got from the whole presentation. It came off like everything's more or less ready to go already, they're just spacing out the releases. I guess it depends on if we get another Intel 16" at the end of this year. In that case i would then assume yeah we won't get an ARM 16" till end of 2021 so there's a nice solid year between them. But if Apple skips a Intel 16" release then i think it's possible that a 16" ARM could drop anytime in 2021 to reset the yearly release schedule to be when they want it to be.
I'd be wary of buying one of the first ARM machines. Lets not forget the first Intel Macs were only supported from 10.4-10.6. Back then of course the releases stuck around longer (10.6 wasn't replaced until 2011), but I'd still prefer they work out the bugs first. Since my primary workflow is through Final Cut and Pixelmator I'm curious to see just how powerful these new machines are.
In terms of the usual first gen products being buggy thing, i think it may be not as much the case with this particular scenario. Just because Apple's silicone isn't actually new, they've been working with it for years and years already. It's not actually first gen, it's taking something they've already had and just expanding on it. Not to say it'll be perfect, but i think it will be less buggy than people assume it will be. Devs get their kits this/next week though, so i'm curious to see what they say over the coming months.