Source: Reddit: Brave new world official trailer: Thoughts on why they cast an 82 year old Harrison Ford as Thaddeus Ross/Red hulk

I’ve always wondered why they’d cast such an old actor. Considering he could retire from acting at any moment.

My theory is that towards the ending of Brave new world Prez Ross gets assassinated during his speech at the White House, as shown towards the ending of the official trailer. He’ll be shot dead but the “other guy” will spit it out. This would be a reference to Bruce when he said “I put a bullet in my mouth but the other guy spit it out” and that sequence would parallel both their lives, considering Ross has once hunted Bruce like an animal only to become one himself.

After the Red hulk gets unleashed (as shown behind the podium as shown towards the end of the trailer) Ross permanently transforms into the red hulk, similar to Bruce.

I have a feeling this movie will be a one-off from Harrison Ford. He’s probably doing it just to leave his mark on the MCU, similar to how other A-list actors have in the past. That way, marvel studios can retain the CGI of Red hulk for all future projects and most importantly, the character will always be associated with a Hollywood legend.