Everything seem to be pointing to the Beatles on iTunes.
I would just ask everyone to keep some perspective here- the Beatles are @#$%^ing huge. They were the second-highest selling artist of the 2000s (source). This is THIRTY-FOURTY YEARS AFTER THEY BROKE UP. They are the most popular band in the history of the world. iTunes is the biggest single music retailer in the US (maybe world, I'm not sure.) They would be a perfect fit.
Keep in mind that even though you may not like the Beatles, you may already own all of their albums (as I do), you may own as much Beatles as you want to; other people don't. People that aren't very familiar with them but would buy a few songs, people who have been waiting for them to be available online, etc. The Beatles have never been featured in a "convenience buy" form before- with the immense popularity of a number of their songs, it is easy to see why this could make a huge impact.
For those saying that the Beatles on iTunes would not qualify as "unforgettable," remember to look at this history of this. Apple and the Beatles (through their business side, Apple Corps) were engaged in heated legal battles throughout much of Apple Inc's history. In fact, one of the most recent battles was around the launch of the iTunes Store (source.) This made it seem impossible that the Beatles would ever be on iTunes- even entertaining this possibility shows how far this has come. Those that have watched how these battles have developed, and have watched rumors about this for years now, know how much this would mean in the context of this contentious history.
As for the size/seeming importance of this announcement, this seems perfect. A keynote address dedicated to this would be somewhat ridiculous, and would warrant justified criticism of Apple manipulating and controlling the press. There are no other events around this time of year that this could be added into. A website/iTunes homepage teaser of this seems pitch-perfect. Also, look at the time- it's very unusual for Apple to to business before more of the company is awake! It does seem like a good time to flip a switch on a server cluster, though...
Also, the subtle teasing in the clocks and song titles is interesting, keep in mind that Apple wants to display actual times on those clocks- George's arms don't line up with any time zone in the world. The others do have striking similarities.