The most interesting part of that trailer was when they said there are two men claiming the songs are theirs and they showed one guy barefoot and one guy in dark shoes. Paul McCartney was barefoot and Ringo Starr was in dark shoes on the Abbey Road album cover.
I was thinking it could possibly be John and Paul, since they both wrote the songs, and technically John wouldn't be dead if they never became famous, but your explanation sounds right.
At any rate, this looks like a really good movie (for once).