No, that's not how it works.

If the court's decision that says laws against inter-racial marriage are illegal is reversed, then any state that wants to can make them illegal. That law does not apply only to "new" marriages. It would apply to all marriages within that state. There is no grandfathering involved unless the new law specifically provides for it.

E.g. if it was legal to own a polluting car and a state passed a law against polluting cars, all the old cars would be subject to that law unless the law itself specifically exempted them.

That's how it works.

--David Grace