I doubt it's a publicity stunt, it's more like NBC not knowing what the hell they're doing and screwing Conan over. Leno should've been let go for good after his contract ended. I've never been a fan of his, and I don't blame him entirely, but I doubt without his persistent whining they never would've given him an earlier show and the whole mess wouldn't have happened.
At this point though, even if he gets the Tonight Show back, I think the ratings would still tank. All the old people who used to watch it before going to bed have probably just been confused by the host changes, and been disgusted by Conan, and have switched over to Matlock. Most the people who actually paid attention and watched it for some semblance of comedic value will probably realize Leno is a huge douche if he takes the show back. And as for Conan, with all the things he's been saying about NBC the last week, I doubt he'd want to stick around much longer even if they kept him as host at the same time.
I rarely watch late night talk shows at this point, but Conan was my favorite for a good 8 years, and he's still hilarious. Ferguson is alright, certainly has his moments. Letterman, well I'd probably get flamed if I said what I thought about him, but I'm not a fan.