I don't think it has taken off like people thought it would - in fact it may have see its peak a while ago. I expect these cards to tick up leading into the world cup. If they don't that's pretty much it for soccer imo. Vinicius Jr. played for Real Madrid, won a title and for the first half of the year was their best player and he's only 22 years of age. He gets to showcase his talent for Brazil in November( Haaland does not as Norway did not qualify).
McKennie is probably the US' best player after Pulisic. The Optic cards should have some decent value as they are condition sensitive. The pop reports show that for most the 2018-19 Rated rookie cards.
The pops are relatively low given the product has been out for 4+ years. I've had 10 base Optic Vinicius JR. and could only send 1 in and it got a PSA9. They were horribly cut and centering was ordinary as well.
Alphonso Davies base Optic pop: 805, PSA10-133 PSA9-513
Vinicius Jr. pop: 956, PSA10- 442, PSA9-476
Phil Foden pop: 1041, PSA10- 499, PSA9-501
Jadon Sancho pop: 1548, PSA10- 341, PSA9- 845
Kai Havertz pop: 1051, PSA10-328, PSA9- 607
Weston McKennie pop: 512, PSA10- 221, PSA9- 232