Originally posted by zapp The current 560 has several flaws, on the other hand it is not that old, so let’s not jump around in circles too soon. A long fixed focal length lens for FF is missing. A large (decently large) aperture tele line could be missed as well (I miss it, not everyone needs it). So yes, good news. New TCs with new tele glass would be nice, but COVID will slow down the process and reduce how much we would be willing to spend.
Collapsible design, modular concept like Leica-R, diffractive optics, 300&600 mm...
I personally think something small and compact, similar to Nikon's 500mm phase fresnel design, around the 500/600mm focal length would be good. They (Pentax) have an, from what I read, excellent 300mm f4 so if they update the coatings and update the motor to the new ring or DC motors, I think they would nail it. Why reinvent the wheel when they have a good product.