PC gaming is not going anywhere. In fact I think with the new consoles (XBone, and PS4) it will actually help the PC gaming scene. With the previous consoles a lot of games were created for consoles and ported to PC with only DX9 support. Now that the new consoles are out and they use x86 hardware and support DX11, the "ports" to PC games won't really be ports at all. There will also always be those PC exclusive games, as there are Xbox and PS exclusives as well. Most PC gamers I know also have a console.
I don't think the phone/tablet games will have any effect on this market since the types of games played on those devices are pretty basic and are usually driven by ad revenue or micro transactions. I don't really play those games...