Now it is probably the worst time to consider switching to Sony. Why do you want to do that, if you already have plenty of lenses which will continue to function well with these new cameras.
You can see from the R5 and R6 that Canon now provides the cameras that are more like what people wanted initially, so now you can get an EOS R or EOS RP to experiment with, and upgrade later. The R system is looking great now, all things considered.
Colour science is such a subjective matter, but I prefer the how the R file looks (but I guess anyone with enough experience can make a Sony look very good) and and also how the body feels over the A7III, particularly the screen and EVF, which are much nicer to look into and operate.
I guess it depends on your photography needs/interests and budget. To me, Sony has never seemed more appealing, to be frank. The A7III seems to offer much of what the R6 offers (not all, but enough at least in terms of specs for my purposes), and the Sony is substantially cheaper than the R6 in my part of the world. And the lenses available for the Sony system (albeit often third party) are far more appealing to me than what Canon is currently offering. For example, the Sigma 85 f/1.4 DG DN for Sony is much cheaper, smaller and lighter than Canon's RF 85 f/1.2, and still seems to be very good optically, which makes the Sigma a much more enticing proposition than the Canon. The Tamron 70-180 f/2.8 is not much more than half the price of the RF 70-200 f/2.8 (and a bit smaller and lighter, albeit 20mm shorter at the long end), and again seems to be optically very good. Sigma's 24-70 f/2.8 DG DN for Sony is highly regarded, and it is signficantly less than the price of a Canon EF 24-70 f/2.8L II let alone the RF 24-70. And the Sony system has small primes which seem to be pretty good, like the Sony 55 f/1.8, which currently don't have any real Canon equivalent. (Canon's EF 50 f/1.8 STM is a very different lens. We''ll have to see what the rumoured RF 50 f1/8 is like when it gets here.) I understand the RF lenses are fantastic, but the cost and/or size/weight savings on offer in the Sony system more than outweigh any optical advantages of the RF lenses for my use.
So, am I mvoing to Sony? No, at least not yet. I've really enjoyed my Canon gear over the years, it would cost me some money to get the lens kit I'd really like, and I am not convinced about the size/ergonomics or EVF of the Sony. (To be fair, I'm not convinced about any EVF yet. I haven't had a chance to try out an R5 or R6 yet though.) However, assuming I move to a mirrorless camera one of these days, I will have to decide whether to stick with Canon or jump ship. At least at the moment, Canon's pricing is not making that decision easy. In fact, I've basically lost interst in any new gear for the time being. Even the original EOS R is still selling for significantly more than I paid for my 6D or 6D II, let alone the R6 which is currently sitting at about a 5D series pirce where I am. And if I spent the money on a body now, I'd still be using my existing lenses so I wouldn't be getting the benefits of RF lenses now or at any time in the foreseeable future, limiting the benefit of the new body. Hopefully the pricing will settle down, and hopefully Sigma and Tamron and others will start making RF lenses, so the Canon system starts looking more attractive to me again by the time I am seriously looking at upgrading from my current gear, but I will just have to wait and see.
EDIT: I've said the same sort of thing as my post above in a few other threads, so I'm going to try not to say the same things again in future (will try not to sound like a cracked record!). I am struggling though with the value of what Canon is offering at the moment. Yes, I know I can use EF lenses on an R system body, but if I buy a mirrorless camera body I will certainly have one eye on the native lenses available for it.
