But you do read it a lot in reviews, things like "this lens uses the popular 77mm thread so you don't have to buy more filters" and "this lens uses an 86mm thread which is bigger than the one it replaces so you'll have to factor that into the pricetag".
I remember I was annoyed when I had my 15-85 with 72mm threads, and a 72mm CPL, then I bought the Samyang 35/1.4 which had 77mm threads. I was only using it on APS-C so I just used a step-down with no vignetting. I also used my 67mm 70-300L with step-up rings to the 72mm CPL, and all my other 52mm and 58mm lenses with a 58mm CPL. But eventually I got sick of that and just bought a B+W KSM 67mm, and found a second-hand Hoya HRT 77mm CPL too (and a 52mm KSM for $20 second-hand recently too).
Then I got lenses with 82mm and 86mm threads, like a wide-angle MF lens (which is fine putting it on aps-c, but then I wanted to use it on native MF). I had to make a decision the other day, buy an 86mm CPL (normal price $200 for a B+W) or a 95mm (a Heliopan second-hand on ebay $100), when I realistically will never have a 95mm lens (unless I win the lottery and buy the Zeiss 15mm). I just went the 95mm and a step-up ring, it's just future-proof so i'll never have to worry about sizes again.
I'm sure there will be the complaints when canon releases the next lens with 95mm threads from a few people. But honestly, even retail a good CPL is only $300 max in that size, compared to what, a $3000 lens? Noone else uses the coloured filters anymore, they were mostly only for B+W film (I use them for B+W film), and GNDs like Lee and Cokin X-Pro you just buy another $20 adapter ring to your kit. So maybe in the film days it might have made a big difference (like see the entire range of Takumars all use the 49mm thread except for the extreme speed/lengths) but these days not so much because it's only one new CPL that you have to worry about.
If you have to take a new CPL into account when you make your pricing decision, then do so, but I don't think it would stop canon from releasing the lens, it'll just make a few vocal whingers come out on the forums.