It makes sense in a “Well, isn’t that just how it is?” kind of way, to me. Though having it in writing worries me to a degree. I could see major publishers pushing for more online situated games and marginalizing further the singe-player component of half-and-half games now that they’ve got “proof” of it being better for sales.
This kind of echos the nagging worry I got reading a few stories a while ago about single player games coming to an end. (A good portion of the links to the stories are here.) Though for the most part the author of the linked-to article considers having multiple people watching a person play a game where only one person can play at a time, possibly swapping controllers and providing input on decisions, a multi-player game.
Still, I really can’t see single player only games dying, but I can definitely see publishers pushing for more online whether or not it comes at a sacrifice to the offline bit. I think hell would have to freeze over before we would lose our Metal Gear Solids and our Final Fantasies. (Unless you count FF11, but you get my point.)