I don't know why Marvel would be under any obligation to pay them though as the agreement was with another company. Credited sure but I don't know why Marvel would pay them royalties as they have no contract with them. It sucks that they can't still make money on the reprints (if they made anything at all) but I just don't see why Marvel is about to kick down everyone's door to hand them a check. The shit's been around for 30+ years so I have a hard time seeing them track down the old teams to do this even out of the kindness of their own heart.
Marvel is good about getting back older talent though. The company does pick up the old creatives to do new work and to me that'd make more sense to negotiate a contract with them then.
But yeah as much as this sucks I just don't see them paying it given they have no reason to honor that agreement since they're not Darkhorse.