It doesn't really matter if they shot DS9 on IMAX film, the market just isn't there to justify the cost of a full restoration. Remember that they've remade a lot of the FX shots, which is a tonne of money right there, and they've remastered the audio too. TNG has the audience to justify the cost, DS9 and Voyager don't. About the best we can hope for is a "best of" DS9 with some of the better episodes remastered (I'll take at least half of the 5th, 6th and 7th season episodes in a heart beat), but there's no way that they'd sell enough to justify a full restoration.
I'd love to be proven wrong, but I don't think it's gonna happen.