The new Avengers: Endgame TV spot had shown us four of the Avengers-Natasha, Steve, Bruce Banner and Rhodey walk out of the Avengers facility, and they look towards the sky at something very mysterious. Many fans have been contemplating about what or who they may be looking at:
1. Iron Man & Nebula
One guess is that Tony and Nebula make their way back home. It is now a given that these characters will make it back with the help of Rocket Racoon and Pepper Potts. So if it is a ship with Nebula and Tony, they might even see Pepper and Rocket aboard this ship.
2. Captain Marvel
Yes, we all know that Captain Marvel will be in the upcoming crossover, but we do not know where and how the character will make her appearance. So maybe, Captain America and his team may be looking at Captain Marvel making her entrance.
3. Thor and Surviving Asgardians
While this is pretty unlikely, Thor may actually find his people, and because Valkyrie will be inbound, this may be them making their entrance to unite with the Avengers.
Another unlikely scenario is that it is Thanos. The Mad Titan would have no business having to leave his haven and bring down a ship to the Avengers facility, but he is capable of making an entrance like this.
5. The “Greater” Threat
From many reports and even toy leaks, the fans know that there will be another villain involved and they may be a greater threat than the Mad Titan. So this may be the threat that arrives at the front of the Avengers facility.