I've never known the PS1 to have expanded much or changed alot, as far as I'm aware all that happened is everyone who previous had a NES, or SNES, or Genesis bought a PS1. Yeah the userbase was older, but that was cause it was 4 years since we got our SNES for Christmas...
You can see today that Sony (And now Microsofts) market is pretty much those now full-time job people who grew up on the SNES > PS1 > PS2 type progression for the most part, and they've pretty much left Nintendo to snap up the new generation of younger gamers with the DS and WIi. Whenever I'm in a GAME store there will always be a few preteens there, and they'll never be looking at anything but the DS or Wii shelf.
The PS1 did 'legitimize' gaming to some people though, I remember all the people who scorned me as a 'nerd' when I talked about Zelda or Metroid at school a few years later raving up FIFA and FFVII. They aimed their marketing at older people and alot of idiots suddenly weren't turned off at playing with what was a toy, but it was hardly a completely overhaul in mainstream opinion.
