It looks like both SIGMA and Tamron are transitioning fully to mirrorless lens mounts, which was obviously an inevitable outcome.
According to Nikon Rumors, this information comes from a large retailer in the UK. We have seen big discounts on SIGMAs ART lenses over the last year, so we expect at least some of those lenses be discontinued.
In total, 18 SIGMA lenses received the axe, and Tamron cut their lineup by 22 lenses.
We do think that we’re going to see RF mount lenses from both SIGMA and Tamron in time. It’s not simply about Canon, both companies have to be able to develop, manufacture and support new lenses on a new mount and make money doing it.
Discontinued SIGMA lenses
Sigma 4.5mm f/2.8 EX DC HSM
Sigma 8mm f/3.5 EX DG Fisheye