All Argentina need to do is qualify. If they manage to do that, which is by no means a sure thing and also manage to make it out of their group, anything is possible.
I have no doubt in my mind that a team like Argentina with the firepower in attack they posses can catch fire for 4 matches and take the World Cup. International matches are generally low scoring anyways and Argentina have proven not to concede too many goals in past major tournaments. Nobody expected Argentina to do jack squat in Brazil either, but good defending and timely goals carried them all the way to the final.
There are still 9 months left until Russia 2018 and a lot can happen between now and then; Sampaoli can figure out the tactics, Dybala and Icardi could turn out good, or Argentina can get a favorable draw.
Anyone writing of Argentina's chances of winning the World Cup (if they qualify) needs to have their head examined. Each team only plays a maximum of 7 games. There are no two-legged ties, nor is this tournament a league. Any team with star players can catch fire or get a bit lucky before the tournament and go on to win the entire thing.