Some market pundits claim that a camera system's mount is its greatest asset. In fact, the mount usually binds a user to a system much more strongly than a single camera body - because people usually invest more money in lenses than in bodies, and the lenses usually stay in use longer.
For the manufacturer or inventor of a mount, however, the strategy towards third-party manufacturers is particularly important. On the one hand, you don't want to have any third-party lens manufacturers on board at all, so that you can skim off high profit margins in the high-margin business with your own lenses.
On the other hand, it can also be worthwhile to grant alternative suppliers access to one's own mount if they expand the existing mount portfolio with interesting models that one does not or cannot offer oneself.
Canon had not openly licensed its RF mount to third-party manufacturers in the past, and 
also seemed to take action against unlicensed RF lenses with autofocus recently.
But now Canon might bring another vendor into the RF boat with Sigma after all. At least that's what Canonrumors suspects, which according to an unknown source has now received multiple hints that initially two Sigma lenses for the RF mount are to be launched in the next 6-8 months - a fast mid-range lens as well as a zoom lens.
Without knowing more, Canon Rumors more or less blindly guesses a Sigma 50mm f/1.4, as well as a Sigma 17-50mm f/2.8 OS DC. At the earliest, there should be more certainty here in the pre-Christmas period. The same goes for another rumor that Tamron may and will also offer lenses for Canon's RF mount in the near future.
;)