They pretty much double their places and North America is to get more spots than South America.
"The proposed breakdown would comprise: Europe 16 teams (13 currently); Africa 9 (5); Asia 8.5 (4.5), South America 6 (4.5), Concacaf 6.5 (3.5), Oceania 1 (0.5), Host nation 1 (1)."
https://www.theguardian.com/football/2017/jan/10/48-team-world-cup-fifa-plan-2026