By leaks, I'm assuming any and all important information released about the games. Knowing the release date, starters, legendary mascots, and the region basis is where I'm at. I will personally shut off and remain off Serebii once the June information is revealed (probably later, just before the July information comes around).
That way, you won't have to be spoiled on the new Pokemon, new characters, region, plot, special extras, and stuff.
I completely shut off Pokemon from 2003-2007, so finding and picking up Diamond Version was like a WHOLE new experience because I had no prior information about the games, and it made them super exciting to play! So that's why some people, myself included, want to avoid leaks. Hopefully Serebii puts spoiler tags/cuts on the information revealed through official outlets even...