Kamara has been capped three times by France and was called up for its latest round of UEFA Nations League matches this month.
However, the 22-year-old had to withdraw from the squad after injuring his knee during Villa's 1-0 win against Southampton on 17 September (AEST).
It was revealed last week Kamara had suffered ligament damage, and Gerrard announced on Saturday (AEST) the former Marseille player will not recover in time for Qatar 2022.
"Boubacar will be missing until after the [FIFA] World Cup, unfortunately, so that is a huge blow," Gerrard said at his pre-match press conference ahead of facing Leeds United.
"It's not ideal. We have had better days on the injury front."
Villa has also lost fellow marquee signing Diego Carlos, who ruptured his Achilles on just his second outing after joining from Sevilla.
Kamara's international team-mate Lucas Digne sustained a heel injury while away with his country and "will be unavailable in the coming weeks".