Would apple ever consider re-releasing Logic Pro 9 if the demand for it was great enough?
I would doubt it.....
It's an old product (it's been almost 30 months since the last update and over 5 years since it was originally released) and so is considered EOL these days.
It doesn't utilize the modern OS X routines.. which is why some people have issues running it under Yosemite....depending in their hardware.
The Logic Dev team are focusing purely on LPX.....
So no....
You can still purchase LP9 however, via places like eBay as part of the Logic Studio 2.0 FULL DVD version...
Note: Dont buy any Logic Pro 9 download or single app LP9 only versions (as they are all illegal/fakes/pirated copies) or the Logic Studio 2.0 UPGRADE packages.... (As they need you to have also purchased Logic Studio 1.0 too in order to be able to install 2.0)
However, as newer OS X versions are released it probably wont be long until LP9 fails to work on any of them....