It seems Kojima is planning to show the E3 gameplay demo of Metal Gear Solid V: The Phantom Pain this Thursday, probably during the next Kojima Station episode. On Twitter, Kojima said:

E3 gameplay demo received much better than expected. It was closed-door & video shooting wasn’t allowed so it hasn’t been revealed yet.
Wanna see?
TPP is free open world game, it’s hard to give u a presentation. The more u get hands on, the more u get to know such freedom & amusement. With that said, it’s disadvantage to show it in limited time at the show unlike Linear game that can be presented like a movie preview.
I shall ask Tan if he’s available Thursday to show off.
While it doesn’t look like it’s set in stone yet, there’s a good chance we will see at least part of the gameplay demo in the next Kojima Station, on Thursday. For those who don’t know, the ‘Tan’ Kojima is talking about is Tan Ziang, who also played the gameplay demo during E3.