This has been predicted since the 90s and has failed to materialize. It has failed to materialize further in the current generation of gaming consoles, which aren't even ahead in terms of hardware to PCs anymore: the chips and processors powering the new generation are approximately mid-level graphics which can be obtained today. Not in the near future - but now.
While what we consider "the PC" may change, it seems pretty apparent that the future is more platform diversity using off-the-shelf components, not less. So long as people still game with a keyboard and mouse, on a machine they might also use for other things, "the PC" as a gaming platform will exist. And with the current trends, it seems likely that PC market-share is only going to increase.