I've been watching the last 3 seasons straight through on DVD, and I don't think they need to be remastered. Maybe for HD like an above poster said, but not in terms of visual effects. Even nine years later, the visual effects still hold up very well today. I've watched the space battles in
The Way of the Warrior,
A Call to Arms,
Sacrifice of Angels, and all the other big space battle episodes and they still continue to amaze me with the wonderful quality of awesomeness in them. The visual effects hold up incredibly well and I don't think they need to be changed. Maybe the only one that I would change (if at all, but even that's not really a must) is
What You Leave Behind where they had spent the rest of their budget and had to use a lot of stock battle footage, but even that is pushing it.