I never said it was valid or that it would work. But I would be willing to bet money that the Left will attempt to portray this opinion (Which was, in fact, quite well reasoned) as proof that he has pre-judged the case. They will put it at the center of a campaign to force him off the next anti-pledge suit that comes around.
Remember: Libs don't care if a thing is true or right. They only care how it makes them feel. They will try to use this as propaganda against him.
Thomas is not weak-willed. It is unlikely he'll give in to the pressure, but pressure there will be.
I won't say your prediction is impossible, but I really don't think the left wants to go there. Justices tip their hands all the time in concurring and dissenting opinions.