Even in the first film, it's kind of used where Ben is not present; notably in the sunset scene (Although an alternate score exists that's on some soundtrack albums) and as part of the throne room music that closes the film.
Yoda's theme is also used in some scenes in EMPIRE during the escape from Cloud City (Most notably when Luke encounters Boba Fett and falls into the trap). Although one could argue that it's being used because Luke now has better skills because of his training with Yoda, so Yoda's 'presence' is felt.
However for some reason it's also used in the AOTC factory scene, although the score to that film was really screwed up anyway in editing (I've heard it's partially because Lucas edited too much after the score was already complete, but also Williams was over-worked that year, hence very similar music being played in Harry Potter and The Chamber Of Secrets during the Quidditch scene).
Interestingly the Emperor's theme also developed from being 'his' theme to pretty much a catch-all for the dark side, such as when Anakin confesses to Padme about the Sandpeople.
I'm pretty sure that the music in this trailer is actually a new composition. Sure it's the Han Solo and the Princess music, but with a lot of choral backing to it that was nowhere in the OT. One of the early TV spots-the one with the First Order base in a wide shot-also used Battle of the Heroes from ROTS, causing some uproar (It also showed that some of the First Order tech is actually repurposed ROTS CG models, as we've discovered with the toys as well.
Although since a lot of TFA seems to use Ralph Mcquarrie concept art for the OT (For the X-wings notably), and some of that concept art was also used for ROTS's vehichles, I suppose it was inevitable.
On a side note, the belief that Disney is ignoring the prequels is a myth. The Marvel comics are using references to them at every upportunity, half of the last Darth Vader issue was set on Naboo, and Luke's fighting General Greivous's bodyguards over in the monthly. Pretty sure Shattered Empire visited Naboo too!