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I don't think a Samyang 50/1.0 is likely, it's just one of the few things Samyang could do to make a potentially hot-selling lens in the already crowded fast-fifty market. Samyang's other offerings have succeeded by filling niches where comparable lenses weren't available for anywhere near the price (how many decent 24, 35, or 80/1.4s, or 14/2.8's, are available at even twice Samyang's price?). On the other hand, the 50/1.4 market is saturated with solid performers starting at ~$15. A new lens at 50mm has to be pretty special to succeed; super aperture is one possibility (in line with Samyang's previous propensity for fast lenses).
Nikon incompatibility is a major setback for such a design. On the other hand, the Canon market alone, plus all mirrorless, is not negligible; furthermore, a "trimmed-down" 50/1.2 for Nikon could probably be made with nearly the same parts (and wasn't the famous Nokt-Nikkor an f1.2 lens, so Nikon mount could accomodate that?).
Still, a 50/1.0, or any 50mm lens, seems an unlikely near-term addition to Samyang's portfolio.