A new lens patent for EF 600mm f/4 DO IS USM lens was recently filed by Canon. The patents could easily visible that are racing through different sites. What kind of lens is that? The lens is super telephoto prime DO lens. See the patent image below.
The another happy news from canon is that the EF 400mm f/4 DO IS II USM lens, which they were announced in the previous year is now at stock of Amazon at the price $6,899.