Of course it is still relevant unless the ADA decides to make changes, which the have hinted at for several years in the Biology, but that could be years away. As I tell my students use the most current material available because a few more questions correct in a section can make a huge difference in the final DAT Score, do whatever possible to avoid a retake.
If you are not taking the DAT until next year, I would focus on your classroom studies, to keep your GPA as high as possible.
Wishing you the best..Nancy, co/owner, Orgoman, DAT Destroyer