The upgraded Daleks that made their debut in Doctor Who's fifth series episode "Victory of the Daleks" and appeared again in the final two episodes are not replacing the more classic-looking Daleks that appeared in the previous seasons, according to Doctor Who TV in a piece about Doctor Who: The Brilliant Book. A quote from showrunner Steven Moffat suggests that there will be kind of a Dalek hierarchy.
“The fact is, we’re not going to lose the old Daleks. We’re keeping them. They’re coming back. We’ll just use them all at once, and have different ranks. All I’ve done is give the Daleks an officer class.”
That's a relief and a bit of a surprise, since the first act of the new Daleks was to destroy the Daleks that paved the way for their creation.
Moffat had previously said that although the Daleks might take a break until there is a really good story for them, when they do return there will be "different kinds". The new ones (that some have begun referring to as iDaleks because they do kind of look like Apple designed them) seem to have ranks that are designated by color: Drone (red), Scientist (orange), Eternal (yellow), Strategist (blue), and Supreme (white).
While I wasn't entirely opposed to the new designs, I wasn't quite ready to let go of the classic versions that the Russell T. Davies era Daleks more closely resembled. I like how the flamboyant colors of the upgraded versions remind me of the Peter Cushing Dalek movies, and I'm sure the idea of having more Dalek action figures to peddle to Whovian collectors had something to do with their creation. I am glad Moffat is keeping both versions active.
On a related note, the BBC trailer below has a tiny bit of footage from the upcoming Christmas special. There are literally only a few seconds, so I didn't think it merited its own post. But interestingly, all three actors who have portrayed the Doctor since the series' resurrection appear in clips from various upcoming BBC shows.