i dont think it will sell that well, maybe similar to the ac/dc and aerosmith packs.
To be fair i really dont have a clue, im kinda against the idea of a rock band beatles game, mainly because i play guitar and the songs, although excellent, are quite easy. you'l get the whole band experience but not much of a challenge.
Something like Guitar Hero Metallica is a lot more appealing; perfect for the kind of people that play those types of games. But i suppose its good to get a good variation!