I wouldn't worry about this very much. The case revolves around a
scriviners error, where one clause of the law refers to state exchanges regarding the subsidy plan, and the context makes it clear that the subsidy calculation and payments are intended to apply to all policies purchased through all exchanges. A reasonable person would draw the conclusion that this was a simple oversight in the construction of that clause.
It is entirely possible that the court, appellate court, and even the Supreme Court might arrive at an unreasonable conclusion and direct that Congress must clarify the intent of the law, though. (As lawyers, they are extensively trained in the art of straining at gnats.) They pulled this with the Lanham Act as I recall. It would be a very odd result, though, with only residents of selected states eligible for subsidies. This might result in residents of other states pushing for a change to the law, or failing that, for their state to start it's own exchange.