You know, you can all say things like: "They will be where they will decide to be. And we can't know what their decision will be", and "[John Lennon] did many good deeds, and that's what God likes to see. I'm sure he's there".
But really, when it comes right down to it, whether or not you go to heaven or not is determined by whether or not you believed that Jesus Christ is the son of God and was raised from the dead for the remission of sins. I wouldn't have a clue what the Beatles as individuals believed, but to keep the argument valid, it must not be ignored that there is only one way to get to heaven, that is through Christ.
The truth of the matter is, that if they weren't Christians, they aren't going to heaven, or are not in heaven. For example, if George Harrison really did follow Indian Mythology seriously, that's a pathway to Hell.
I'm sorry to have to put it like that, and I love the Beatles very much... but there's no mellow way of putting it.