Combine that with the fact that Marvel Studios is releasing the Doomsday trailer earlier than it released any other Avengers trailer and more recent rumors ( via The Hollywood Reporter 's Heat Vision newsletter) that there will actually be four trailers released over the next few weeks,

The Steve Rogers we saw in the trailer could be the one we last encountered in Avengers: Endgame or he could be an entirely different variant of the hero. His story was said to have ended a long time ago, which is why Falcon and the Winter Soldier and Captain America: Brave New World were such important movies.