After group stage, the difference will be the round of 32 instead of round of 16, so there's one more round after all
And the classification will be 2 best teams of each group + 8 teams with better 3rd place.
I bet Fifa will chose this rules next year, it makes more sense.
Groups of 5 teams is very unlikely because there will be 48 teams
FIFA was earlier thinking about having 48 teams divided in to 16 groups. There will be three teams in each group and the top two will progress to the round of 32. But then, Qatar 2022 worked well with 4-team groups. Most of the matches were fiercely competitive. So they may go with 12 groups of 4 teams each. The top 2 teams from each group will progress to the next stage, and in addition, 8 among the 3rd placed teams will also qualify to the round of 32. In my opinion, I find the modified format (12 groups) much better than what they had earlier.