Oh, this again. Fun fact: It's been longer since WPVI tried changing music (27 years) than it was from when they started using MCTYW to when they tried changing it (24 years.)
Only on TVNT will a graphics package or set that's older than 5 years be declared "ancient", but a music package used for 50+ years is something that shouldn't be touched. A lot has changed in the last 27 years (namely declining viewership!) and I suspect that a subtle modernization of the music (the 1996 version was anything but subtle, it was a drastic change that tried to make MCTYW into a serious, The Mission-style orchestral news package, which it is definitely not) wouldn't result in the "riots in the street" people around here like to imagine happening.
We know they have selection of 615-made cuts they've been using for a few years now, I would imagine most viewers are now used to hearing "the music" that's not specifically the 1972 version.