I think promising a new better Trax hurt their sales, but it might be a good time to get a great deal on remaining 15's (if any still exist) with the 100K warranty or a 16.
I really don't think anything changed except some sheet metal and some trim items on the 17.
If you are disappointed with the trim on a Trax you should look at the Encore, I liked my 15 1LT Trax very much but it was very plain compared to the 16 Convenience Encore.
I am a Chevy and Pontiac guy always owned one or the other, but this Encore beats the crap out of the Trax in the same trim level.