This is actually a really interesting case. If you go by legislative history and the understanding of what it mean when it was passed, Title VII should not protect sexual orientation or gender crap.
If you go by textual interpretation, "sex" at the time was also interpreted to mean gender. So, progressives might argue that a textualist should say it prohibits discrimination on the basis of "gender", which means trannies should be protected. However, the way they use "gender" now is different from the meaning back in 1964, when it was understood to mean the same as biological sex. So, true textualism should reach the same result as "original intent".
It'll be really interesting to see what Roberts does. For political reasons, Democrats should probably hope that the decision goes against them so they can make it a political issue moving forward by pushing for a new law.