I use PNG all the time. It's my favourite image format for web graphics. I am really hoping it doesn't die out. Or at least mozilla and other browsers continue to support it for the sake of the few that do use it. Alpha transparency effects rock :-)
As for Ogg Vorbis, that might do well when hardware starts supporting it... Check this out:
Ogg officially official; Vorbis finding its way into hardware players (Arstechnica)
