From the look of the new longer trailer it seems like the future world predicted in the first two Terminator movies (I have blanked the travesty of the third from my mind) has been altered.
I was hoping there would be some kind of cross-over or interplay with the excellent TV show Terminator: The Sarah Connor Chronicles. I thought I spied Stephaine Jacobsen who plays the suspicious human agent, Jesse, sent back from the future in the trailer (around 1 min 30 secs in) but imdb doesn't corroborate that idea. The fact that Season 2 of the television series is full of potential double-crossing and suspicion of John Connor's motives led me to think that the future the previous films promised had been changed significantly following the time traveling antics of the humans.
There could be lots of scope to explain the roles of Riley and Jesse in the movie but I guess the producers will ring-fence the two franchises and keep them relatively independent of each other. Shame, as Summer Glau makes a good Terminator
Oh yeah, there's also a video game tie-in dropping in May 2009