To be honest, I don't think it was ever intended for this to release this year. MS just wanted a good showing to help drive sales at Christmas, I'm expecting Recore to be next unless it's a smaller title advertised like a AAA title. And just to give this comment some context, I didn't think Uncharted 4 was ever going to release in 2015 and I'm doubtful about Horizon: Zero Dawn too.
The PS5 Exists.