I think the PC has already become unprofitable for many (Valve are one of the exceptions, and they clearly see writing on the wall). There are very few PC releases that aren't primarily console titles.
PC Gaming is alive and well. It's just that they don't spend millions on marketing themselves. Minecraft, GoG, Diablo 3, WoW, LoL all are standing examples that PC Gaming works.
The average age of the games you listed is 4 years old. Is that really proof of a market that is "alive and well"?
Going by release dates (which is how we normally gauge console games' ages), League of Legends is about three years old, MineCraft is about a year and a half old (a lot of people forget this because it had both an open alpha and open beta, unlike any console game I know of) and Diablo 3 is not even one year old yet. Their average age is less than two years unless you're counting time in development, by which standard GTA V (due to release late this year) is like three years old.
You missed one (WoW; 2004).
Whoops! Indeed I did. Sorry, I think my brain mentally blended it with the other initialism in the list.
To be fair, it throws the average way down and also it isn't entirely fair to use the 2004 date since they have been releasing expansions throughout the life of the game, but I still don't think the original list is a sign of a healthy overall market for PC games (though it is proof that the right game hitting the right market can still make a significant amount of money on the PC).
Granted I have no numbers, but between the convenience of Steam, the seasonal sales, and the fact that it's trivial to use an Xbox 360 controller on a PC...I just don't see this. Why would they bother releasing on PC at all if it wasn't profitable? If anything, it seems like more console games than ever are getting cross platform releases on to PC. Personally, I'm seeing less and less reason to own a console at all. My xbox is really just a netflix player these days.
If the desktop PC disappears for the average user, I wouldn't be surprised if even ports stopped getting released.