Some rumor that they're going to appear in Thor 3 but 90% of rumors are fake so take that with a grain of salt.
And anyways, there's no reason they can't shill both. Although they're both extremely Kirby, the Inhumans are more secret alien-like civilization whereas Eternals are more Marvel's New Gods. But the way they handled the inhumans push (fucking horribly), I wouldn't trust Marvel to not botch an Eternals push. Only Marvel writers I'd trust to write them are Ewing or pic related.