Re: Canon R5 or R6 Mark II or something else altogether...
This is just an opinion but the R5 is still quite state of the art and quite a bit superior to the R6 Mk 2 if you deeply crop your images or shoot high resolution video.
Firmware 1.6 has essentially eliminated the R5's 4K and 8K overheating issues (8K raw can overheat at about 40+ minutes). There is still a 30 minute limit on continuous record time on the R5 that has been removed on the R6 Mk 2.
The Canon R6 Mk 2 should have a bit better low light performance (less noise) than the R5 (about 3/4 of 2 stop) but this noise difference is easily eliminated when needed with the Topaz DeNoise application.
If you don't crop images deeply, I generally believe the R6 or R6Mk2 is a great option.
If you shoot wildlife such as birds in flight and need to crop deeply, the Canon R5 is likely the better choice.
As I understand it, the R5 is still a top seller against competition in Japan and globally. Further its mechanical shutter life is rated at 500,000 vs 300,000 for the R6, which may or may not matter to you.
Since Canon has essentially eliminated the R5's overheating constraints and the reality that the R5 is still quite competitive with Sony and Nikon offerings, I'm not sure I see a strong motivation for Canon to release the R5 Mk 2 immediately. They may chose to extend the life a bit longer (pro cameras used to be kept in the market a bit longer than enthusiast cameras).
If your budget is constrained or if you enjoy changing camera bodies often, the R6 is a superb choice. If you keep camera bodies a long time, the R5 might serve you a bit longer as you may need the extra resolution over time.
You can't really lose selecting the R6, R6 Mk2 or the R5.