True, and precedent is always subject to change. But, the fundamental difference between Roe and Texas v. Johnson, from a cons utional standpoint, is that the argument for deeming flag burning protected free speech is a much more textual argument than the privacy fundamentals that drive Roe. To say that flag burning can't be supported by the First Amendment, you'd have to write your way around the text of the Cons ution or declare that "speech" as used in the First Amendment is a limited concept that doesn't include expressive conduct (so that, for instance, writing or expressive artworks aren't within the protections of the free speech clause).
The power of Scalia's view on flag burning isn't the result itself; it's his belief that protecting a person's right to burn the flag is an express, textual matter.
Roe lives on a much slenderer reed of cons utional interpretation, since the privacy interests that are used to support its conclusion are rights that seem implicit in many of the protections in the Bill of Rights but aren't expressly guaranteed in the same way that a right to free speech and expression is. As a pure matter of textualism, overturning Roe could be as simple as saying there is no express cons utional right to privacy and certainly not one that encompasses a right to abortion. It certainly won't be resolved that simply, of course.
Ultimately, I don't think the cons utionality of abortion and flag burning are particularly equatable.
The Second Amendment arguments are, to me, mostly about how far you can stretch the word "infringe," but even those arguments are almost purely textual.