IIRC, someone with connections recently said that DS9 on Bluray is basically "now or never", and that the people in charge really want to do it, but they don't know if they can get the math working well enough to give themselves an excuse to do it.
Basically, TOS on Bluray was a big risk, but they figured it had a chance, so they took that bet and it paid off. TNG on Bluray was an even bigger risk, but they gambled and won again.
DS9 on Bluray is a bigger risk than TNG, because DS9 got smaller ratings and has fewer mainstream fans. The hardcore fans are reliable, but they tend to like both shows and there aren't enough hardcore fans to make either show profitable. DS9 needs support from large numbers of nostalgic casuals in order to work. So DS9 has the same costs to produce on Bluray as TNG, but it will obviously make less money, and the rewards for the risk of TNG were already small.
Apparently the best hope for DS9 is for TNG to earn some more money. If you're on the fence about buying TNG, now is probably a good time to do it. Don't go out of your way to buy two. It won't make a difference, and there's no sense in flushing your money down a toilet to try and send a message.