^I suppose that's possible but they fit 7 (!) episodes on one of the discs of Supernatural: Season Three Blu-ray set and, to my eyes, there was no problem with quality. The show only has a DD 5.1 track but I would think that if they can fit 7 episodes on one disc then there shouldn't be a...
For what it's worth, shows like Lost and Heroes have 5 episodes per Blu-ray disc so I'd imagine that this release could do at least that many too. Although I guess that could vary based on where and how the original versions are on there.