Yeah Kennen as well is another top lane popular choice for top laners should they want to play carry tops.
Rumble and Gnar will continue to be the go to because they're champions whom even if they fall behind, they still have the capability to contribute significantly in team fights and map presence:
Rumble because he only needs Sorc and Guise to get going with a ton of damage.
Gnar only needs frozen mallet to become an absolute monster to deal with.
We've also seen Poppy as well whom with her CC lockdown, can very easily secure first blood on a TP or jungle gank.
Basically this entire Worlds meta is all about top laners, support, and junglers who all can put down good early game pressure, GP just simply does not have any early game pressure until level 6 with his ultimate. So even though his late game is crazy good, its just too risky to try and gamble with teams who are all oriented towards such strong early game pressure.