From what we can tell, the Pokemon World Tournament is not going to appear in the anime at any point in the near future.
But let's say it does happen.
Let's say Ash goes there and enters the Type Expert Tournaments.
Supposing that he needs a minumum of three of each type Ash could currently enter the Normal, Fighting, Flying, Ground, Fire, Water and Grass tournaments.
My question is, which tournament do you think he would do best in? Not necessarily which he wins, just which he would do best in.
And don't forget, his pokemon in the flying tournament won't just be his birds. Charizard and Gliscor can enter there as well. And the fighting tournament would see Infernape, Pignite, Scraggy and Heracross coming together.
Personally I think the Ground tournament would be where he would shine best, given the variation his collection of ground types show.
[P.S. I'm not entirely sure that this is the correct place to post this. If it's not, let me know and I'll correct it.]