If I had a dollar for every time I get an email with that question!
I - like everyone else here - would love DS9 to be remastered in HD next. However, it would be a massive project, far more involved than TNG was.
The simple fact is that there's no news at the moment. Naturally, there's talk about it - but that's all; there are no plans in place and no project has been greenlit. CBS-D are still entrenched in TNGS6, and will still be in TNG mode for a decent amount of time to come.
Why more involved than TNG (outside of those fleet shots)?
I'm wondering the same thing. Considering CGI has been used for years, I would have thought it be easier than taking the original film negatives.