It’s very likely that this will be cinematic and not show actual Madden 18 gameplay. The short video will likely use the in-game engine, but it will be closer to what you see in replays than it is the final gameplay.
A better opportunity for Madden 18 gameplay videos and screenshots will come at EA Play in June. This is an event by EA that runs around E3 where gamers can come to experience the new EA games.
You shouldn’t count on a Madden 18 demo that you can play on your own PS4 or Xbox One, but if you go to EA Play you will be able to play Madden 18 early.