i think they have to be the "official favorites" until someone beats them in a major tournament. but i don't think they're the most likely to win. if they did, it would be amazing...a first. but it's hard to sustain that kind of success over time, particularly when there are other good teams out there. injuries, aging and a little bad luck here and there inevitably take their toll at some point.
of course, this spanish side is young enough that its nucleus will still be around at the next world cup, so who knows?