According to a report published by The Phoblographer, Sigma has filed patents for three new zoom lenses: a 300–600mm f/4, a 400–800mm f/8, and a 180–800mm f/5.8–8.4.
The 300–600mm and 400–800mm ranges aren't ones I’d consider for myself, as they seem to be aimed at photographers who need long reach without the need to also capture subjects that are much closer. The 180–800mm is more appealing for that reason—it offers more flexibility.
The bad news is that there’s no mention of Canon RF mount versions. It appears these lenses are primarily being designed for the Sony ecosystem.
The first Canon mirrorless camera using the RF mount was released in September 2018, and here we are in 2025—with still no widely available third-party lenses for the system, despite ongoing rumors of a possible release from Sigma. This pushes Canon users to buy EF-mount lenses and adapt them to the RF mount, as it remains the only viable option for purchasing lenses that are more affordable than the newer RF lenses.
Is this Canon’s marketing strategy the right one? Apparently, yes—because it hasn’t changed since 2018.