If you need something soon the R5 with the 100-500 might meet your needs. I don't shoot low light very much so I don't know how the R5/100-500 would do indoors, but I have been very happy with it. The problem with the RF tele-converters is the amount of the front extends into the lens. Even with the 100-500 the lens must be extended to at least 300mm for it to mount.
At long last and with a lot of advice (all apprecited) I went with the R5 and the Canon 70-200 L ISII 2.8 w/ an adapter. I chose the Canon 70-200 L ISII 2.8 over the new lens because:
The RF lens might be really cool but I do not think it is substantially better than the II.
I would have gotten the III but it is not available,
But the main reason is:
The RF lens extends out of the body of the lens and retracts into it - and I should 80% outdoors. That means 80% of the time I am exposing the outer half of the lens to dirt and pollen and then retracting it back into the lens. That can't be good. The II is fully encased. I may lose a little, but I think the gains are great. And the II with an adapter was about $1,700 and the RF lens is $2,700.
So... shortly I will be shooting the R5 with the Canon 70-200 L ISII 2.8 and the extra battery/handle.
Give me a couple of weeks and I will let you all know how that turned out.
"The RF lens extends out of the body of the lens and retracts into it ..."
I doubt that is a serious problem or even a problem at all. There are many examples of lenses that do that. There has been for years and years. The Canon EF 24-70mm f/2.8L II USM Lens extends and retracts upon zoom too. It is likely the biggest selling Canon lens of all.
Thank you ebiggs and jrhoffman... I will wait until I can't wait. And I will report back once I have shot the R3... or the R5 if I can't wait. I appreciate the guidance.
Congrats on the new purchase. Check to see if the R5 has a crop mode, which I think it does. You may not need or want to use the teleconverter in crop mode.
I have the Canon EF 70-200mm f/2.8L IS II USM Lens. I have had it for years and it is my second most favorite lens ever!
It is a fantastic lens and the best 70-200mm ever made. Well, I suppose the III is a tad better with the new lens coating. People make light of just adding a lens coating and calling it an upgrade but in fact it really is an improvement. It is a difficult and expensive process to apply and it does help in certain situations.
BTW, if curious the Canon EF 24-70mm f/2.8L II USM Lens is my most favorite and most used lens.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.