Canon Rumors reports that a totally new lens design for a 300mm f/2.8 is out in the wild for testing. The new lens is reportedly quite a bit lighter and smaller than the EF mount Mark II version.
Canon’s EF f/2.8 300mm lenses have a long history going back to the early 90s, with each successive generation earning a reputation for being among the most sharp of all the current lenses.
The new RF version is rumored to shave off as much as 40 percent of the weight and 30 percent of the length. That would put it at about three pounds, versus the EF Mark II’s five pounds. The EF Mark I was six pounds, and the non-IS version before it was 6.3 pounds.
All of those lenses have retained value more so than even most Canon L-class lenses. Even as the lens has been discontinued, used EF 300mm f/2.8 IS Mark II lenses fetch between $3,500 and $5,000 on the used market.