It is very hard to speculate on the future but looking at this current Argentina team I don't see them even progressing beyond group stage without messi, if you look at Argentina record with and without messi the stats shows they hardly win matches without him. Argentina have always been a country that relies on individual brilliance that's y there greatest success was during the time of Maradona of the blessed memory and subsequently now with messi. If Messi do retire after this then Argentina will pray to have a player with same characteristics of these but without that then it will be hard. I am not disputing the fact that there exciting players coming up but Argentina doesn't do well as a collective team.
I am sure that on Messi's retirement, there will be players who can take up the responsibility of inspiring the team that he carries. He is a big figure for the team, and they look forward to him, but Argentina to me will still do fine without him, Legends come and go. I watched their game and noticed that other young players playing with Messi still have the opportunity to express themselves on the field with him, his presence in the team with them is not suffocating to their talent. When he retires, the players will mature into the position of responsibility.