10 more hours or so before the Charizardite Y competition ends and the cut off for getting the stone is
~6,5k on mobile and ~22k on 3DS.
It's a bit surprising how few people have entered the competition; about 700'000 on mobile and 60'000 on the european 3DS board, which means about 400'000* thousand for all 3DS regions. Since Diancie was given out to commemorate 5 million downloads, that means than only about 1 in 5 people are participating in the competition, which seems really low since the special stages unlock very quickly after starting the game...
Getting the stone on mobile is way easier; 1 out 3 participants will get it while on 3DS only 1 out of 5 will receive it. On the other hand, 3DS owners can also get a Mega Speedup if they place at the very top while mobile users, similar to the early 3DS competitions, can't.
I placed on the 30'000th spot with an itemless score of 14k and feel pretty safe since the cutoff is 250'000 people. Will still check in the last hour in the unlikely case I fall outside the first 250'000 and do a quick item run.
*Estimate based on the number of prizes given out in each region.