POISSIBLE SPOILER BUT I DONT KNOW!!!!
whoa so the daleks arnt the foe in this one, maybe its called asylum of the daleks because they want to escape someone andwant asylum from the enenmy? thats why theyre the oldest foe?

@Simon

The Daleks are the main foe in this one. The Daleks are his oldest enemy and I assume they kidnap him in order to send him on this impossible mission to the Asylum where these Mad Daleks live and I assume the mad Daleks are threating the universe and even the Daleks themselves, So really The Docotr is forced into helping the Daleks by fighting the old mad Daleks in this Asylum, as even the Daleks themsleves are scared to enter the Asylum of mad Daleks.

@Simon

@Rosey

Note that in the press release it says “oldest FOE”. Not “oldest FOES”–it’s singular. So…who is the Doctor’s single oldest enemy? It’s hard to say, but I suspect the Master, Davros, or Omega. The recent Series 7 trailer lends credence to the Master theory–why would the Doctor mention the Master in conversation to Amy if she had never encountered him? And especially when he mentions Daleks right afterwards…

I’m very excited to see this episode, especially because, from all the spoiler-free reviews I’ve read, the Daleks are actually scary again…to the back of the sofa I go! September really can’t come soon enough.

@Rosalie If you are going to talk about the Master being his oldest doe, then you were need to include the Rani as well.

@Simon
it would be funny if the daleks were running from the silence and need the doctors help this wont be true but it would tie into the whole silence and aliens running from there planets

@Steve
She’s also an option, but a less likely one in my opinion. I sort of doubt that they would introduce an entirely “new” (yes, there are many of us who have seen the Classic series, but many if not most of the viewers today have only seen the revived) villain without at least planting clues to lead up to their entrance/return.
Davros is likely because we’ve seen him in the new series before and because of his obvious connection to the Daleks, but he’s already had a major arc–one which appeared to end with his death. Of course, it wouldn’t be the first time, but still…
Omega, although he’s never appeared in the new series, still has a presence there. The omega symbol has appeared far too many times in connection with the Church and the Silence to be coincidence. However, I think it’s more likely that Moffat’s saving Omega’s return for the 50th Anniversary–the clues aren’t quite large enough yet and a Dalek-centric episode leaves too little time for an introduction to new viewers.
This leaves the Master. He is certainly one of the Doctor’s oldest foes, he’s appeared in both the classic and revived series, and he’s demonstrated his ability to evade certain death to new viewers. He’s mentioned in the trailer in a conversation that, based on Amy’s onscreen knowledge, he has no place in…there’s no one quite as likely as him.
Of course, there’s a very good chance that I’m wrong and Moffat will come up with something entirely different, but I think that the Master could be a logical choice.