Canon RF 100-300 f/2.8 IS USM

[neuroanatomist]

But that there will be a "nice teleconverter solution," whatever that means.
I am excited about the potential of both of those, but have to admit, the 200-500 f/4 is less appealing without the built in TC. So, I'll have to wait to see what this "solution" is.

There have been a couple of Canon patents for TC solutions recently, one quite recent where some elements rotate and slide out of the way in different locations that looks like a two-option solution (e.g. 1.4x + 2x switchable, or perhaps 1x=bypass + 1.4x or 2x). There was another from a couple of years ago with what looks like 1x+1.4x+2x (or a TC zoom) with the ability to also add drop-in filters and maybe a kitchen sink, but that one does not look like something that would be made into a product (in theory it could, because of course 'reduction to practice' is needed for a patent, it just seems rather impractical).

[neuroanatomist]

There was another from a couple of years ago with what looks like 1x+1.4x+2x (or a TC zoom) with the ability to also add drop-in filters and maybe a kitchen sink, but that one does not look like something that would be made into a product (in theory it could, because of course 'reduction to practice' is needed for a patent, it just seems rather impractical).

I read the actual patent for that one (as opposed to the blog post coverage) and it looks more like a mount adapter patent for video applications (matching a larger image circle to a smaller sensor with simple magnification optics, variable ND or image stabilization possibly being added). Not really a TC patent at all.

Meanwhile, FedEx has my 100-300/2.8. FedEx Ground used to be reliably an overnight delivery from NJ (B&H, Adorama), but now it's usually two days for delivery though sometimes they get things to me faster. Two days would be fine if it was fixed, but I'm not a fan of the variability. I live in a nice, safe neighborhood but even so I'd prefer not to have a $10K lens sitting in front of my garage until I get home. In this case, I switched the delivery to a nearby pickup location. Sure, B&H sends things like this as 'direct signature required' but since Covid our regular FedEx drivers ignore that and just leave the packages. Even wine club shipments that require not only a signature but one from someone over 21 are left in front of the garage.