Now that CBS has officially named Tom Snyder heir to the post-Letterman throne-his live 12:30 a.m. show premieres in December-the question remains: How will the 20-year TV veteran fare with 20-year-olds? The results of an informal poll: *The media analyst: ''I don't think it's a natural flow from Letterman to Snyder. David Letterman has a much younger audience. I'm not sure (CBS) didn't blow it.''
*The CNBC staffer: ''His career has defied (demographics). He has always been popular with kids from way back on the Tomorrow show. He transcends age.'' *The program director: ''He deserves more of a chance than some others who've been given the opportunity.''
*The Late Show audience member: ''Tom Snyder is a staple of late-night TV. It's a safe bet for CBS to stick him on. (But) I like Conan O'Brien better. I'm a cynical Generation X member who doesn't appreciate prepackaged, corporate, late-night TV.''
*Dave himself: (Onwhat kind of demographics he envisions) ''We're shooting for nursing homes.''
