Canon: We are in talks with other [lens-]manufacturers

My own translation of the relevant quote.

Q. Many photographers are waiting impatiently for the RF mount to be opened up. At present, Canon is the only brand to maintain exclusive control of its mount. Are we going to see RF lenses from other manufacturers in the near future?

Tetsuji Kiyomi. It is true that we have been approached by numerous third-party manufacturers. We are listening to their requests. However, we do not have any particular strategy or policy on the subject of third-party lenses per se. Naturally, I can't share any more details with you, but what I can say is that we will approach things on a case-by-case basis according to how they align wit hour strategy. I can't tell you more.

Go Tokura. One example of this is the launch of an RF lens by Cosina [the Voigtländer 50mm f/1 is the first [authorized] "third-party" lens to communicate with the camera body via the RF mount – ed.]. We are currently in negotiation with other lens manufacturers. That is the situation at the present time.

So, they acknowledge Cosina as an official licensee and they say they're in negotiation with other manufacturers. I'm pretty sure those manufacturers include ones that make lenses with AF. It so happens that Cosina doesn't. But there's no way that Canon is not negotiating with, e.g., Sigma on the subject of RF lenses. Sigma said they were investigating it; Canon says they are now negotiating with third-party manufacturers. So I'd strongly suspect that that one is at least on the table. With Tamron specifically, it's harder to say, but it's possible.

Now, I think all of this does lead back to questions about what an "open" mount really is (and I don't think the FE mount is really fully "open" either, for the record, considering the limitations Sony places on third-party lenses, and that's even considering their relatively open attitude towards them).

But whatever. Anyway, I think we'll see the following in the near future:

1. Sigma RF-S primes (the same trio we have seen already on EF-M, and which just launched on Z). These would certainly be welcomed by many R7/R10/R50 users. I think these are likely to be some of the next new third-party lenses on Canon cameras, given Sigma's stated interest, what Canon has said and the status of RF-S (incl. vs. APS-C Sony and Nikon)/the existence on EF-M.

2. More Cosina Voigtländer lenses. Though of course the existing ones for M-mount are adaptable pretty easily. Manual-focus lenses, naturally, but all the lenses this manufacturer makes are, so that's not weird.

Things I am pretty sure we'll see eventually:

3. Sigma full-frame RF lenses, in the same optical design used on the L/FE mounts. Although Sigma's EF offerings remain very strong (and are in my experience a bit better on R bodies than F/EF Sigma lenses on Nikon or Sony bodies with the FTZ or MC-11 adapters), they have a few standouts I'd be interested in (like the 35mm f/1.2 or maybe their new 150-600). Still, this is a larger lineup than their APS-C trio and hasn't been taken to Nikon yet either. I think they will come eventually, but they're not going to be the first Sigma lenses we see, I imagine.

Who knows, but probably?

4. Tamron lenses? See other people's comments about Tamron in particular.