It would appear that UNIT are due to make a return appearance later in this series of Doctor Who – in Episode 11 (entitled ‘Turn Left’).
Below is a photo of two extras from one of the shoots, and they are quite clearly UNIT soldiers.
Also, if you look closely at the wall behind these Daleks (from the "Coming soon" trailer), you can just about make out the winged globe that is the UNIT logo.
And finally, this photo from Doctor Who Magazine shows a UNIT officer and Rose. What is interesting is the uniform worn by the officer – why is she in a dark one and not the standard khaki green?
In reality, it would appear that she is wearing a uniform that the British Army calls “No. 1 Dress Ceremonial Uniform”, seen below on an Officer Cadet at Sandhurst.
But why this UNIT officer is wearing it (and with a beret not a peaked cap) remains to be seen…