In the press release I received this morning, Sigma mentioned that they will introduce a new lens during the PhotoPlus show in NYC at the end of the month:
Sigma Corporation of America, a leading still photo and cinema lens, camera, flash and accessory manufacturer, will showcase its full line up of Sigma Global Vision lenses, including a brand-new addition to the line, at the upcoming PDN PhotoPlus Expo 2017 held at the Jacob Javits Convention Center in New York City from October 26-28, 2017 (booth 837).
Sigma is rumored to announce a new 70-200mm f/2.8 lens that will replace the current 70-200mm f/2.8 EX DG OS HSM version (see also this recent patent).
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