Smart watches will eat some quartz watch market share and some mid-range mechanical, but the cogent smart watch criticism applies: that it doesn't provide enough of a functional delta over a phone. People who want mechanical watches want mechanical watches. Otherwise they'd already be wearing a more accurate, more functional and less fussy quartz watch.
As an aside, in an ironic development, a Belgian mechanical watch maker (Ressence) has produced the best design I have ever seen for a smart watch:
http://ressence.eu/collection/type-3/
https://pbs.twimg.com/media/CGmnh0_UYAANb_j.jpg
Available for the bargain price of 20-40k...
If a smart watch maker ripped this design off, and made the bezel touch-rotatable... Well, I might change my tune a bit.