There are vast differences between different types of gaming. You have MMOs, which generally require a dedicated computer and not a massive amount of processing or graphical power. Modern FPSs such as the Crysis series are extremely taxing, and therefore more likely to be played on a system that costs more from a manufacturer/distributor or was custom-built by the user.
Then there are your Call of Duty style games which are FAR more popular on consoles simply because the buy-in and hookup is easier than PC-side -- you don't need TeamSpeak, matchmaking clients, dedicated servers, etc., to have a fun time. You only need to "plug and play" and hop online; the game itself will cost you $10 or 20 more than its non-console counterpart, but the hardware on which its running is at most half the price of a good gaming rig...and you probably already own an HDTV so that's not extra cost out of your pocket just to play.
Then we consider mobile or tablet gaming. Angry Birds and Words With Friends don't need all that real-estate, even though an iPhone or iPad (or equivalent device) may cost as much or more than a console. You play them anywhere, any time...and that's great for someone who can't or won't commit the time to a 45 minute MOBA match, a 2+ hour MMO raid, or dozens of hours on a single-player RPG or hack-and-slasher.
The TLDR is this: whether consoles have hit their "high point" and are on the decline is irrelevant. They're still going to be around because they are geared toward a different type of gamer than many other platforms. They'll change shapes, sizes, capacities and functions...but they'll continue to exist in one form or another.