This is not a good way to judge or predict anything. Things change, and not necessarily the way you want. We 'always had' an affordable Mac Pro that started at $2500...until the day it started at $5000 instead.
Personally I see this bigger iMac getting the same processor as the 16” MBP, which would be more in line with the relationship between the previous 21” and 27” iMacs.
An iMac that gets the same system as the upcoming MacBook
Pro will be an iMac
Pro. This isn't complicated.
it will need an even higher performance chip, closer to whatever they’re going to put in the AS Mac Pro.
No, it doesn't. There are no rules to determine that. The old iMac Pro was a stop gap performance wise ahead of the Mac Pro and was $4000+. The next iMac Pro will be much cheaper.
After nearly two decades, why would Apple suddenly force the two 21” and 27” groups into one?
Because they can? Because consumers overwhelmingly buy the cheaper 21" model and now get a much better 24" model to replace it? Because Apple isn't going to make an entire product to fill a tiny niche which is consumers that want bigger and better (but not
that good)?
It’s certainly possible the larger iMac will be a “Pro”, but it’s not likely in my opinion for the reasons stated. In any case, it’s clearly far from clear.
You have not made any "likely" statements here.
"I want" is not an argument that makes it more likely.
"They used to" is not an argument that makes it more likely.
Here are the arguments that matter that dictate what is coming:
1. The
reliable leakers state that the bigger iMac is very big, indicating much bigger than 27". In all likelihood, this means 32". 32" 6K display = more money = no longer in the realm of the old 27" iMac.
2. All of Apple's Apple Silicon releases point toward a very strict return to consumer and pro differentiation with less cross over than before. The consumer machines have all been released, with the M1. The next products on the horizon are all Pro machines. If a consumer iMac with a screen larger than 24" that sports an M1 existed, it would be for sale right now.
3. The move to 24" for the consumer iMac, like it or not, is a dead giveaway. You don't get to ignore this important fact because it doesn't agree with your preference.