Anyone have any insight as to how they decide what will and won't have a TrueHD track?

It's easier to put them on recent movies, but it takes time and money to do a TrueHD track, so they're not going to put it on every release.

Definitely on the major blockbuster titles, ie Batman Begins and Superman Returns. Probably Harry Potter 4 as well. And probably for action titles that would benefit, such as Troy and V.