in the gaming industry right now, it might be a really good choice. multiplayer is a neccesity in games today; you rarely see games without it anymore. in fact, you almost never see it anymore! i know people (my uncle, for example) who don't even bother with the campaign anymore; they don't even start it. i think if valve can keep up their history of good multiplayer games, they'll do just fine.
I think it's a good decision. If L4d can get so much publicity, who knows what else they might come up with. I have to admit, home front was a bad game to make though.. e-e