I think whats happening is some or all & of the following:
1: MS Game Studios do not care enough about PC gaming as they know it would cost them a lot of money to make serious inroads so they just throw out mediocre stuff like AOE Online & MS Flight (both F2P but around £80 each if you want all DLC content
Doubt many PC gamers are prepared to pay so much for an inferior experience). MS were prepared to let Remedy self publish Alan Wake on PC which is a crazy decision considering how many copies its sold in a few days
Good luck to MS on Windows 8 having native Xbox LIVE support all it will mean is its easier for developers to bring some content to PC I cannot imagine it will be much more than an embedded XBLA store on PC though.
2: XBLA is a massive PIA according to many developers & MS now charge $40K per patch which is insane
I realise they want stable well tested games but its driving developers away to Steam/PSN which is only good news for PC gamers everywhere. (I expect Alan Wake American Nightmare on PC within 6 months for instance
3: Steam allows publishers/developers to have confidence & if the game is good it will sell either at launch or when its very cheap.
4: Many console owners are making the jump to PC gaming as the games are so much cheaper & technically a long way ahead. Xbox LIVE is ruined by all the adverts/rage screaming children. PSN was never any good to begin with & as its F2P unlikely to change much (the publishers have to pay for it though
).
I think PC gaming is growing rapidly worldwide as a lot of big countries like Germany, Russia, Brazil, China, Korea only like PC gaming. This is driving a lot of growth (not in UK though as PC gaming is apparently declining a little). I do not think next gen consoles will make much difference to PC gaming as they are unlikely to offer anything more than current PC's can manage anyway. Current gen consoles cannot even handle 720P without vsync disabled on a lot of games so next gen will likely offer 1080P with more detail & thats about it. There will probably be an 18 month period when next gen consoles are out where PC gaming may take a hit though unless the games are very easy to port over