It's a loss. Trump did not work his way through district, appellate and the Supreme Court to argue for a delay in complying with subpoenas. He argued for immunity from complying with subpoenas. The court ruled against him. He lost.
That part confirms no man is above the law. It is a legal point, a finding of the Court, that rises above all election cycles and campaigns.
On the political side, yes it is true that Trump's tax records (which are typically and voluntarily released by almost every other presidential candidate) are unlikely to see the light of day until after the election. As I said above, that is of little consequence. It seems likely that Trump is going to lose the election. His tax records becoming public or not will not change that.
