There might also be some fans waiting for the boxset of all seasons to come out.
Wow. I shudder to think how much a boxed set of 7 seasons on bluray would cost. I walked past a set of one season of TNG in Target the other day, and I had to do a double-take when I saw the price tag! But for some reason, I don't think I'd have the same reaction if I saw DS9 on bluray. I'd fork out the cash faster than you can say, "Dabo!"
Also, bear in mind that no studio in its right mind would ever in a million years release seven years' worth of brand-new television series Blu-Ray product all at once onto the market as a boxed set at full retail cost.
They'd never sell enough copies to break even, much less turn a reasonable profit; the sell-through costs at launch for the individual seasons are already substantial, and seven
such seasons dropping at once would be far out of most Trek
fans' price-range, to say the least.