Interestingly the 4th Circuit Court of Appeals just reached the exact opposite conclusion today about federal exchange subsidies in a parallel case.
Justice Roberts already had the chance to kill the ACA and he instead sided with the liberal justices more than a full year before the law went into effect. What makes you think he is suddenly going to change his mind now that it would directly effect those already receiving subsidized insurance?
The Supreme Court has heard many cases that argued that some law or act should be be limited or null due to clerical errors in wording. In every case the precedent has been that they should be interpreted based on what the true intent of congress was rather than by the typo.
In this case many other parts of the act reference congresses obvious intent to create subsidized Federal exchanges. This ruling is ridiculous on the face of it and it will be overturned, don’t panic yet.