Yeah, can't see it happening in R1's first few weeks- it would detract attention from R1. However, could be a good ploy a few weeks down the line. Would help bump up the box office later on 8)
Can't see Disney unleashing a EpVIII trailer until the New Year, at least.
They've yet to reveal the episode title and would be conscious of confusing the average movie punter with too much Star Wars.
Probably looking at a trailer being attached to something like Beauty and the Beast (in March) or definitely SW Celebration in April.