I'm sure as many people who prefer SST nostalgia over the current incarnation that sales did pretty well, it's just that WB isn't exactly the best company for DVDs, especially as far as children's/family compilation sets are concerned.
Oh yeah. Sure, they try to make fans happy initially, but then they either suspend making them all together or, like they did with the Smurfs, release the beginning of the sets perfectly, and then they cut to kiddy volumes of 5 episodes for twice as much as they'd cost in a season set. Hey, I'm still waiting to hear if they're going to even continue the Tiny Toons, Animaniacs and Sylvester and Tweety Mysteries sets.
Unless SW has fully control of the DVD's they plan to release, I'm worried about the whole thing myself. I feel the only reason why there hasn't been an OS 3 was because SW had that new 40th anniversary set, and while it doesn't exactly count as an OS, it would indefinitely compete with it if they released both at the same time. Plus, I'm starting to think they only planned on making 2 OS sets anyway.