I am surprised no one has made a thread on this. The Department of Health and Human Services is proposing to define "sex" as immutable and fixed at birth, and to excise gender identity from protections based on sex, and seeking to get other federal agencies to do the same in the hopes that it will stand up to lawsuits. Courts have tended to defer to federal agencies in how they interpret the law, as long as the interpretation is reasonable, and given how successfully McConnell has packed the courts, they may very well uphold this.
The idea that "sex" doesn't cover gender identity seems superficially reasonable, since the difference between sex and gender identity is one that trans activists make themselves, and superficially reasonable may be enough for John Roberts. However discriminating against people for being trans means discriminating against them for not fulfilling the roles expected of their biological sex. To do otherwise is to essentially argue for a "separate but equal" standard. For this reason, courts have interpreted "sex" as including gender identity and gender expression for a long time, so it is also possible Roberts might consider this jurisprudence to take precedence.
This ruling also has some interesting implications for intersex people, insomuch as we were clearly not considered here. The DHHS has proposed that disputes will be resolved by karyotyping. Given that many people have a Y chromosome but appear and identify as female, or an X chromosome but appear and identify as male, this could theoretically lead to ipsogender intersex people being assigned to a gender different than the one that they were assigned at birth and identify with. In practice, given that it would only apply to disputes, it looks like it will allow some intersex people to be recognized as a sex opposite the one they were assigned at birth if they so choose, though I am sure that was not the intent.
I assume that when they went with karyotyping rather than the more popular and much cheaper "if you have a penis, you're a man; if you have a vagina, you're a woman" it was not because they recognize that a growing minority of intersex people with ambiguous genitalia don't have them "corrected" at birth. The generous explanation is that they realized that it would be incredibly unpopular to have official genital checkers. The less generous explanation, and the one I suspect is the main driving force in light of the other changes, is that it would allow trans people who have had bottom surgery to be classified as their gender identity, and we can't have that now.