UPDATED^2: List of proposer season 4 and beyond theories

Here are the most common theories:

Forge is dead permanently. Revenant is the only season 4 legend.
Forge didn’t actually die, or he did die, but will be respawned or brought back in another way and he will be back either in time for season 4, or in time for the mid season break. Forge may also come back in a later season. He will recover and return at a later time.
That wasn’t forge who died. The forge in the interview had a scar that the poster didn’t have, and he looked slightly different (possibly due to art styles). His eyes are a different color in the poster than in the interview. In the leaked image of Revenant, Revenant is holding a metal skull. Maybe the metal skull is the skull of the fake Forge that died. Forge will be back either at the beginning of season 4, or at the mid season break.

Forge is dead permanently, but we’re still getting 2 new legends for season 4. The other legend will be DUMMIE.
Forge is dead permanently, but we’re still getting 2 legends season 4. The other legend is Loba. It wasn’t Revenant who broke into the Hammond Robotics lab, it was Loba, and she stole their equipment and is on her way to World’s Edge. This one is most likely false based on the latest OTV tweets.
Forge isn’t human. Forge is a robot created by Hammond in an attempt to pass a robot off as human. They are all simulacrums with Forge’s memories, and when one dies, or gets defeated, they just bring out a new one. Revenant is the original Jimmie McCormick, and hates Hammond and the imposter Forge’s for stealing his life and likeness and that’s why he killed “Forge” on live TV
Crypto and Revenant are working together to take down Hammond and the Syndicate. This one could really work with any of the other ones.
Revenant is Dr Hammond, the founder of Hammond Robotics. According to the lore page, no one knows what happened to him. It also says his son was working on weird robot biology stuff. Revenant is either Dr Hammond or his son.

If you have any other ones, put them in the comments and I’ll add them to the list