The film seems to be following one of two scenarios: either the Beatles never existed as a group, or everyone forgot about them. If the Beatles never existed, just how much has been affected by this? Do people remember Layla? Did the band members ever meet their wives or good friends? Do their children exist?
The implications from the trailer seem to be that John (barefoot) and Paul are coming on the talk show. It's very probable the band the Beatles broke up early and they went on to less successful careers. John might be an indie songwriter with a weird streak and Paul McCartney the frontman for Wings in this universe.
Jossed. That's a nightmare Jack has at one point. John does appear towards the end, living in a house by the sea.
There is a third possible scenario but it doubles as a possible Downer Ending, the trailer shows during the power outage Jack gets hit by a bus, this film could just all be a Dying Dream/Adventures in Comaland type thing, the second possibility is less downer however as he may wake up and realise his Love Interest is all he wanted all along or something.
The Reset Button is surprisingly averted. Jack continues on with his life in the new reality, having learned some lessons, but the world remains changed.
It's highly possible that George Harrison is still alive in this universe as well, especially considering that cigarettes no longer exist and George died from lung cancer.
Unless, of course, he simply smoked cigars to fatal excess.