It happens from time to time.
After talking to a couple of sources that didn't chime in on the announcement date, they did seem to think that the Canon EOS R3 was going to be announced before 3rd quarter of this year, but that obviously didn't happen.
The postponed Olympics that start this month are playing no role in the launch of the EOS R3 I am told. The real issue is the same ol' issue, production challenges. There cannot be a repeat of the stock issues that the Canon EOS R5 and Canon EOS R6, which wasn't good for business and added to some already negative coverage of both of those cameras.
The Canon EOS R3 will obviously be present at the Olympics, but until Canon can produce these cameras without hiccups, I think it's safe to say that we won't see an official announcement before then.
The next time that I get an announcement date, I'll do better in vetting the information.