Canon wants to make money, and the question is whether there is any money for Canon in making more aps-c primes. Sigma can spread costs and build volume with marketing the same lens with different camera mounts, and Sigma may be willing to chase smaller volume than Canon. So, as always, we shall see what happens.
The interesting thing is that Canon’s M Series is increasing in sales. We can’t count Nikon’s mirrorless line, or Canon’s R line, because they’re new, and so starting from zero sales, they’re growing. But for pretty much everything else for everyone else, the situation is not how popular a line is, but how unpopular it is.
i say that, because we look at every company, and see sales dropping fairly rapidly. So lines that are dropping less rapidly are called “more popular”. That means that the M Series is one of the rare, these days, lines that are actually popular. Which is why, after all these years, Sigma is making lenses for it. Fast lenses that Canon isn’t yet making. My belief is that if these lenses sell well, Canon may look at that and decide that this is something they should be doing.