I have this idea that the R3 will be able to track a specific subject, e.g. a dedicated person ('s face) like the bride on a wedding. This (from Canon USA) sounds a bit like it (last sentence):
The EOS R5 and R6 were only the beginning. Using Deep Learning technology, the upcoming EOS R3 will offer enhanced AF performance and tracking capabilities, with even better face-, eye-, head- and body-detection. And, the EOS R3 will add a new type of subject recognition, for its AF system.