The tl;dr is that, yes, indeed, half of Oklahoma is part of land reserved for the Creek in a 1833 treaty. And almost two centuries of subsequent jurisprudence and state development has (unsurprisingly) completely ignored that with effectively no legal basis. Neither Congress nor the state of Oklahoma has ever lifted a finger to try to make this right.
Basically, this is the Supreme Court saying that enough is enough, this can't go on, and telling the relevant governments to get their shit together and figure this out.
No, Injuns aren't coming for Tulsa.