I think you’ll see France, Argentina and Spain drop off over the next four years, while Croatia, Australia and Canada rise up. Serbia will be there abouts too.
The US will always be top dog, and complacency needs to set in for someone special to come in and take advantage (ala Argies in 2004).
The world game isn’t getting any worse, I think the US are more consistent. And yeah, that’s a challenge the second tier of teams need to respond to.