Now that Sigma now Samyang, and will be calling the Samyang lenses their "Classic" series, I doubt we'll see any auto-focussing lenses from Samyang, and al their lenses will remain manual focussing.
Why would Sigma want another competitor?
As far as cine lenses go, Sigma don't really make any, so using Samyang as their vehicle to get into cine lenses seems a good idea.
Wasn't that an April Fools?
And the teaser photo is just a closeup of a lens they announced along the 10mm f2.8, which is the 8mm T3.1 II. If you read carefully Samyang's "announcement" of the teaser, they do not say they are going to announce a new lens. They are going to "release info on 28 April" about lenses that are coming. My guess is they are just building hype out of nothing, they are going to release info of a lens they already announced.
And about AF, they already stated that those were internet rumours and that they are not planning anything like that in the near future.
(I keep a really close eye on them. I've been waiting for the 50mm for years now.)