Mix of speculation and educated guesses based on evidence. I can explain it too. Show is 2 hours long and Phil Spencer said they will “show first party there in a big way” in addition to third party games.
Jez from WindowsCentral said he expects 3 acquisition announcements at X018 but acquisitions can only fill so much time.
Finally, Phil Spencer said they will talk about keyboard and mouse support on Xbox One during X018 as well as talk about some of the games that support keyboard and mouse on Xbox One. Would be a good time/place to announce their 3 2019 PC games are coming to Xbox One.