Messi's Argentina and Neymar's Brazil could meet in a blockbuster all-South American final in Moscow next July if results go according to plan.
Argentina – runners-up in 2014 – were drawn in Group D with Croatia, Nigeria and debutants Iceland on Friday, while five-time champions Brazil headline Group E, which includes Serbia, Switzerland and Costa Rica.
Asked about a mouth-watering showdown with rivals Brazil which would reunite former Barcelona team-mates Messi and Neymar, Sampaoli told Omnisport: "It would be a dream a final against Brazil. Neymar versus Messi.
"It would be incredible. I hope your dream is fulfilled."
Argentina's hopes of claiming a third World Cup rest heavily on five-time Ballon d'Or winner Messi, who has 29 club trophies to his name but is without a senior international honour for La Albiceleste.
Messi's hat-trick in the final match of CONMEBOL qualifying saw Argentina scrape though to Russia, having faced the strong possibility of missing the showpiece event.
With 16 goals in all competitions for Barcelona this season, Messi's form has Sampaoli's Argentina daring to dream.
"I see Messi splendid, mature, confident, knowing who he is," Sampaoli said.
"For us, knowing that he is in this form gives us one more reason to dream."