would it kill canon to upgrade this to 26mp like the 6Dii?
You can tell the difference between 24 and 26MP? I surelly can't, and I had the 6D II.
I doubt we'll ever see a R6 with higher resolution than a R3/R1. It's probably too soon to assume anything, but the R6 series seems to follow the bloodlines of the 1D and R3 series (baby 1DX3, baby R3...), and it looks like that recipe is working just fine, so...why change and increase development and production costs?
They’re both midrange bodies, used by enthusiasts and pros alike, that aim to offer a wide variety of features and capabilities. They’re more alike than they are different, at least from a marketing perspective. Both cameras drive the lion’s share of full frame sales as well, so they’re critically important to both Sony and Canon
Yes, from a marketing perspective.
I'm not gonna address video, but from a photography standpoint, Sony chose resolution, while Canon is clearly picking speed, specially if the R6 III comes with a stacked sensor.
Coincidentally, I happen to occasionally shoot events with a close friend of mine, who's a sick Sony fanboy (not just camera gear). He shoots the a7 IV, while I shoot the original R6, which has frequently lead to interesting debates.
The fact that each brand picks a different approach makes their respective devices unique. We have here people asking for more resolution. Could they have people, on their side, asking for more speed? Perhaps.
The a7 IV can shoot at 6fps lossless RAW, and 10fps lossy, while we sit at 12fps since 2020 for 14 bit RAW, and increased our 12 bit speed to 40fps.
I would say both are very legitimate approaches.