Argentina will open next year's tournament against Chile at El Monumental on June 12, it was revealed on Tuesday.
Scaloni hopes 32-year-old Messi, who will again be aiming to win his first senior international trophy, plays beyond the 2020 Copa.
"I don't know if it will be the last. Hopefully not," the Argentina coach told reporters.
"But Argentina need the title, more than just him. Hopefully, don't promise anything, but we'll give the maximum to reach the final."
Argentina, who last won the Copa in 1993, will also face Uruguay, Paraguay, Australia and Bolivia in Group A after their opener against Chile.
Scaloni's men beat Chile in the third-place play-off this year, in a game that saw Messi and Gary Medel sent off.
"It's a nice game to start," he said. "Anyone would have been difficult because the debut is always difficult, but this one has a special feeling.
"Chile has always been difficult for Argentina, especially in recent times. Difficult, but we are fine."