[Update (7:45pm ET): In a "clarification" post on Reddit this evening, Robot Entertainment CEO Patrick Hudson said that Orcs Must Die 3 would be a timed exclusive for Stadia, but the company wouldn't say how long that timing would last. This is a relatively standard setup for third-party exclusive games these days.
"OMD3 would not be possible today without Google's support," Hudson wrote. "They are behind the game in a big way. We've hired more developers to bring it to life. It;s the OMD game that fans of the first two games have been wanting, and we’re thrilled that we have the opportunity to make it."]