Taking cues from "Endgame," Paris did seem slightly surprised that Joe's wife wasn't a hologram herself. So I'm guessing this means that (a) Holograms have at least similar rights as the rest of organic beings, and (b) they've got mobility, and Doc's mobile emitter is either cloned, or outdated somehow. Maybe a little portable generator that wraps itself in the holographic display (I never understood why the Doc didn't put the portable emitter *inside* his hologram - hello, then it's protected by the forcefield that is he.)
So, I'd say that there are at least a little minority of sentient photonics out there, and this is likely only aided by the photonic lifeforms Voyager discovered through their long trek home.
At any rate, I'd say yes, they exist. I wouldn't say they proliferate. Holodeck usage might have been restructured: maybe now you get original TNG-level holodecks only: settings and places, not inclusive of high-level interactive holo-characters. Or some sort of "sentience level" testing: maybe once holo-characters reach a certain level of self-awareness, then they're considered sentient critters. Oh jeez, I dunno.
Big kettle of fish, no real idea how to handle it.
The Doc
So you think, 'Might as well,
Dance a Tango to Hell,
at least I'll have Tangoed at all.'
-- "Rent," Jonathan Larson