I do not think it will massively affect the market at all, I cannot see people who like Swiss brands (or Japanese and so on) switching allegiance to this gimmick. Each to their own I guess, I dislike the styling and have no love for the whole Iwatch thing.
If apple brought out clothes, I do not think they would take market share from high end Italian designers - I do think that tec geeks that love apple may invest more in clothing then they would previously, and I imagine it could be the same for the watches.