The PC is not a console to be launched, it doesn't need AAA exclusives ... the PC will simply be there regardless. Ports, RTSs, CRPGs, MMORPGs keep it in existence. MMORPGs if nothing else will keep it so.
In a year Valve might be able to market a DX 11 PC in console form factor for 400$ ... a box which would be able to render say Mass Effect 2/3 substantially prettier than the Xbox 360. With a controlled hardware and software environment it would be be both convenient and plug and play (the gaming OS would in the default install be entirely hidden, the OS in which all official steam games would run and any games specifically designed to integrate with the box's game launcher, any normal PC use and legacy gaming would be done in a virtual OS). Although it depends a bit on how much Microsoft would try to obstruct this.
PS. the casual market isn't a market I'm interested in ... it's an orthogonal issue. It might be the bigger market, it might not be, it certainly doesn't have the games I spend money on in it. You can't service both markets at the same time and for the moment the gamer market is still there and too substantial to simply ignore. You won't pull people like me along into the depths of hell consisting of popcap games and shovelware.