I was a regular Leno viewer before he "retired" and Conan took over, but since he returned, I have just had no interest in his show. It's not that I'm consciously boycotting it or anything, I'm just indifferent to it. To me it's kinda like the "new Coke" of the 80s. It was good, they did away with it, now they're trying to bring it back. It's not working.
Having Kevin Eubanks and his band leave isn't going to help, either. The rapport between Jay and Kevin was part of the appeal of the show, and now that's gone, too.
Haven't been a regular Letterman viewer in years. These days I check the on-screen guide to see who the guests are going to be for Leno, Letterman, and Fallon and record only when the guest is interesting.
Back to the original point, I think NBC underestimated the fallout of their decision. A lot of people who used to like and watch Jay and Conan aren't going to watch Jay, anymore.