I believe With the Beatles, and A Hard Day's Night should be released after Rubber Soul, and obviously the White Album or Let It Be following those two. Then finish out with Help!, Revolver, Magical Mystery Tour, Beatles For Sale, and Please Please Me.
I believe that should be the order, simply because, With The Beatles and especially A Hard Day's Night have their best harmonies, and "classic rockers", geared more towards the vocals and guitars.
I'm sure they won't come along this easy but I'm really afraid Harmonix is going to leave out some of their better RockBand friendly material. If they eventually end up releasing the entire LP collection for the game, that would be splendid.
I'm also pretty sure between the 3 previously announced full albums for DLC they will release a singles pack and probably contain tracks from the Past Masters collection...hopefully The Ballad of John and Yoko, Old Brown Shoe, She Loves You, Long Tall Sally and She's A Woman. Perhaps even Free As A Bird and Real Love, from the Anthology