The latest episode of What If…? finally unveiled the overarching plot that the series is building towards. After Thor made plans for a date, he and the Watcher were surprised by the welcoming of Ultron bots. From a mysterious portal, Ultron appeared in the body of Vision clad in the armor of his former shell. At that moment, the episode ends as even the all-knowing Watcher is confused that a once happy ending would get abrupted by tragedy once again. We, as viewers, are left wondering what his arrival means for the multiverse.
There are a few things we can take away from his sudden introduction. Ultron managed to achieve his goal from Avengers: Age of Ultron by adding his consciousness into the new body. We still have no confirmation if James Spader is returning to voice the character, but he didn’t return to voice the character in Avengers: Damage Control VR and might have moved on from the franchise. Still, there’s some hope they convinced him to return while he is busy filming The Blacklist.
He also is wielding all six Infinity Stones on his body, which he shouldn’t feel any side effects from due to his body not being organic. It also implies that this version of the character most likely succeeded in dropping Sokovia and wiping out Earth. We learn in the Age of Ultron that his primary goal is to create an empire of dust where only metal survives. If he achieved his goal on Earth, there’s the chance Thanos came after him due to possessing the Mind Stone. Once he fuses with the stone, he’ll felt the others and reunite them. It makes him one of the most formidable enemies within the multiverse.
They might be taking inspiration from the time when Ultron became the leader of the Phalanx during Annihilation: Conquest and with the complete domination of the galaxy, he sets his eyes on the multiverse. Yet, not to annihilate organic life but to rule over them in the mightiest position there is. He’s the worst aspect of Tony Stark and believes he can control the future. The best way to do so would be to replace the Watcher.
The reason for this theory is due to one single image potentially teasing his end goal. We see Vision in his Ultron armor floating above a scene. There’s a chance that the next episode ends with Ultron taking the Watcher’s position and narrating the final episode as the now fallen god-like entity summons together with the strongest warriors from across the multiverse. The consequences of him gaining the watchful eye of the entire multiverse but with the desire of intervention. Who knows what he would unleash if he obtained that power. If he wins, no place in the vast multiverse would be safe.