Exactly. YOUR workflow dictates this. There are many workflows that benefit from monster amounts of RAM, but don't benefit as much from CPU speed. And there are many workflows that benefit from monster CPU speeds, but don't benefit as much from the amount of RAM. And then there is your type of workflow which is mixed, and which can benefit from both.
Sure, there are always tails to any distribution, but in my very mixed workload I don't think I'm particularly ignorant of any one type of work. The issue is really just that 16GB is jack squat these days. Interacting with a dense webpage might be using on the order 100s of megs to a gig even, keeping many browser windows open and in active memory can hog several gigs (and well if it goes into compressed memory, it slows you down to go back and use it and you'd really like that added RAM), editing a sizable PDF several gigs. And of course the OS soaks up a few. I'd very much maintain that pushing 6 threads, with really say 12 or so GB of useable RAM is threading the needle (its just 2 GB, maybe a touch more, per thread for pete's sake). So much so that the can-see-sizable-benefits-from-a-CPU-only-upgrade crowd is not a particularly large segment of the population.
That was my point. For CPU performance, it's going to be a big upgrade this fall (assuming it comes this fall). If CPU performance alone isn't enough for you, then of course wait. Just don't say (and I'll quote you verbatim) that this means, "basically means no one should be buying the 2018 model just to have it 6 months ahead for the Cannonlake one".
Your statement firstly assumes nobody needs lots of CPU speed without 32 GB RAM (which is simply wrong) and secondly assumes that Cannon Lake will be out 6 months after the 2018 MacBook Pro (which I'm guessing will also prove to be wrong).
On that second point, you should probably note the first part of my sentence that you quoted, "And if true". Where I was referring to the quote I responding to pasted above my statement that read: "You will see the 2018 MacBook Pro in October/November, then you will see another update in June 2019 with the Canonlake Update." Please, lets not argue about whether or not the conditional statement is true or not. That you won't know, I won't know, no one besides those inside Intel likely knows at this point. However, if Intel knew it was going to be delayed again, they would probably announce it. So, I'm betting its more likely than not their timeline is more or less what's going to happen. The fact that it is possible that Cannonlake Macbook Pros will be more than 6 months out is certainly a good reason to by a Coffee Lake MBP. But
IF we knew for sure it was going to be a relatively short amount of time, I'm betting nearly everyone would hold out on older machines because A) CPU-only updates aren't going to improve the workflows of nearly everyone by much at all and B) the short amount of time between updates makes the marginal utility of buying now vs later very small compared to the gain of having an even better CPU+RAM combination for the entire life of the machine. You bring up 3 year cycles of machines, well, being stuck at 16GB until early 2022 sounds really freaken dumb to me. And a 3 year cycle is pretty dang fast these days. I wonder how 16GB of RAM is going to look in 2024? All and all, you're adding up a lot of conditions for the people in the "not-wait" group (doesn't need RAM now, doesn't think they will need it over the life of the machine which is going to be relatively short at ~3 years, can benefit largely moving from 4 to 6 cores, can't/doesn't want to wait to see if Intel and Apple move to the next platform in short period of time).
Anyway, this is all just kind of a mental exercise. Most people don't pay too much attention to these things and just buy the new thing when they feel like they could use a new computer, even if the 1 year (or 4 year) old model would serve their purposes just fine. Largely the MBP sales are going to regular old consumers, not people that really stress their machines. For what ever its worth, that's why that word "should" was in my sentence that we now need to dissect. And heck even for those people, they are going to "feel" the RAM way more than those 5th and 6th cores. But again, they aren't paying a lot of attention because waiting for the Macrummors page to reload because they have 100 web browser tabs open just isn't that big of deal.