During rolling upgrades, having different versions of Hiberna Search is a reasonable request. At least we should try to do it instead of accept that we can break thing de facto.

Ok, it's a valid use case, I didn't think about that. But as I mentioned, we don't "accept that we can break thing de facto"; we already try not to break things between micros, and probably even between minors. Yours was a very special case, since you upgraded from a beta.