I don't think the Establishment Clause is going to be unincorporated anytime soon. However, I think it's important to answer good arguments. There is a good argument to be made that the Establishment Clause never should have been incorporated. There is also an argument to be made that NONE of the Bill of Rights should have been incorporated, which means that states would be free OR NOT to infringe on all of the Bill of Rights. There is also a good argument that the Privileges or Immunities Clause of the 14h Amendment in fact was intended to incorporate the Bill of Rights to apply against state and local governments. Then there is a refined argument that Justice Thomas is sympathetic to that yes, the P or I Clause was meant to incorporate the Bill of Rights, but not the Establishment Clause.
And that's because "Privileges or Immunities" relate to individuals rights. And whereas the Free Exercise and Free Speech Clauses of the First Amendment do relate to individual rights, the Establishment Clause does not. Rather it was understood, when constructed by America's founders to be a federalism provision. Incorporating the Establishment Clause would be akin to incorporating the 10th Amendment.
That's a good argument.
But here is a more specific answer to that claim that I didn't mention in my last post on this matter. You actually have to get to the end of Prof. Kurt Lash's 71 page article for him to make it. It is this: Whereas America's founders understood the exact words of the Establishment Clause to have a particular meaning, the framers and ratifiers of the 14th Amendment gave those same exact words a different meaning, one that reflected "anti-establishment values."
It should be noted that when John Bingham, a chief architect of the 14th Amendment, said on the floor of Congress "that the privileges and immunities secured by the Amendment were 'chiefly defined' in the first eight amendments, and then fully quoted all of these amendments," he included the Establishment Clause. He just read the first eight amendments verbatim.
We need to stress a point of interpretive contention: The argument is what is incorporated is NOT what America's original founders thought, rather it is what the framers and ratifiers of the 14th thought.
You are going to have to read Lash's entire article for his evidence, but I will provide one smoking gun in favor of this contention. It's on page 50/1133 of Lash's article. The 1857 Iowa Constitution and it reads: "The general assembly shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof...."
Try doing this with the 10th Amendment and see it totally doesn't work.
I know there is more to the argument. That provision of the Iowa Constitution doesn't demand the Establishment Clause in fact be incorporated against state and local governments. But I think it does demonstrate that it certainly is possible to view the clause as something other than a federalism clause.