There's a lot of theories flying around in these early stages, so to whom do you think the title is referring? Who's the Golden Child of TF5?

 

well, since there's only one yellow(gold) bot...

 

I think the dragon is the last knight, but the new Prime could be a disconnected thing to the knights, because if Bumblebee become a Prime why should he be the last (if it is not intended as like the "newer")?

 

I think Anthony Hopkins' character is the knight in question. I think we're looking at a Last Crusade type of reveal.

 

Personally, I speculate that Megatron is the Chosen Knight for these reasons
1.) In the trailer, he's seen with a sword meeting that Lennox (or whatever his name is) guy.
2.) Megatron might be the only one who could stop Optimus.

 

Who is The Last Knight?

 

I am going to go with either Megatron, Bumblebee, or other, but if I have to pick one it's Megatron!

In AOE Lockdown told Prime the Transformers were built to be servants, and that Prime was the last Knight he had not captured. However, since Lockdown was specifically capturing Optimus alive it stands to reason that there was a reason the Quintessons wanted the Knights alive. Since a lot of evidence points to Megatron being a Knight, and it is almost certain Lockdown was in the dark as far as Megatron's survival went, Lockdown probably did not even consider going after a Cybertronian he thought was dead, especially when he was capturing the Knights alive.

Since Lockdown had delivered the other Knights to the Quintessons it is likely that the other Knights are under Quintesson control. Once Optimus gets the purple eyes and ends up not being himself I think at that point Megatron will be the last living Knight not under Quintesson control, hence "The Last Knight!"

Additionally, the movie will explore the pasts of Prime and Megatron, so I suspect that Megatron plays a big role in the film regardless of who the main villain ends up being.

Of course, it's possible Bumblebee becomes a Knight ("Cybertron's newest Knight has a coat of golden armor" or whatever that tweet said.), or that the dragon is a Knight I suppose, but my best guess is Megatron.