I honestly don't have a problem with it. Some games may degrade their singleplayer to have multiplayer, but it's not guaranteed in any way. And I personally felt God of War III was a waste of money when I got it on release. The singleplayer was nice, but at that price I would have much prefered to spend my money on games with more content, so some multiplayer is nice. Provided they make it good of course. My main concern is really whether the multiplayer will be refreshing enough to stay interesting.
And you'll still be getting plenty of singleplayer games. Look at how well Skyrim did for example, or Batman: Arkham City for that matter. They're not going anywhere. But more focus on multiplayer will also bring more innovation to make it interesting for singleplayer gamers. Look at Dark Souls and Journey for example, they bring multiplayer to the singleplayer gamers, and do a fantastic job of it.
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