https://www.cnet.com/news/avengers-endgame-spoilers-just-dont-russo-brothers-say/

The note applauds the fan base that's been on the Marvel Avengers movie ride for over a decade. 

"Please know that the two of us, along with everyone involved in Endgame, have worked tirelessly for the last three years with the sole intention of delivering a surprising and emotionally powerful conclusion to the Infinity Saga," the brothers wrote. Please note the use of the word "surprising."