PC gaming IS dying. Any PC game made today will eventually not sell and barely anyone will ever play them anymore! They will be completely replaced with something different!
They will be replaced by newer, more interesting lines of PC games produced with new tools and ideas, and most likely take advantage of better hardware that will allow things that couldn't be done before.
Along with newer console and mobile games, and players will shift between them as various things strike their fancy.
This is eminently disproved with the existence and success of sites like GOG.com. Games are not replaced. They are displaced by newer titles, but many gamers eventually come back to revisit the games they love. Nostalgia works in favor of the PC. That and emulators...