I think it's worth noting that no matter how many times we've watched the movies and heard Mr. Williams' musical scores, his music is still able to evoke an emotional response even when it's used with scenes for which it was not intended (i.e., the new trailer). Most classical music snobs would probably be dismissive, but I think Mr. Williams is a composer of modern classical music that transcends the movies.
It may have been modified a little, but it was mostly Williams' scores from the Original Trilogy movies. It's common practice to use whatever music might be suitable for trailers regardless of whether or not that music will be in the final edit of whichever movie they're promoting for the simple reason that the movie's actual soundtrack usually hasn't been completed when the trailer is released. With Star Wars that's more difficult because the music is so closely identified to the six current movies, which is why we heard Leia's Theme (for example) in the new trailer--it's recognizable and it created a mood for those scenes, but it may or may not actually be used in the movie.
Struzan retired in 2008. Rumors early on stated he would come out of retirement to do the poster for The Force Awakens, but I don't think that was ever officially confirmed.
Exactly how I pictured it as well in my mind.
