H1b visas have primarily been used by consulting companies to bring in less expensive junior engineers (<$100k) [1]. If new directives make it harder to sponsor junior engineers, it will shift the mix to more senior engineers. This will shift the supply/demand curves, so that US salaries will come down for senior engineers and go up for junior engineers.
[1] http://www.myvisajobs.com/Reports/2017-H1B-Visa-Sponsor.aspx