since corocoro tends to leak even a week before the official release though... would they risk it leaking stuff that's supposed to be huge reveal saved for E3?
I doubt it. If they have huge reveal at E3, they'd save that for next corocoro I think.. especially with how japanese news-sources like that sundayshow and corocoro tend to be behind ever since we've had simultaneous releases internationally. I even feel sometimes like they reveal way too much and way too early officially these years, and I have a feeling it's because they don't want to allow these confusing reactions to leaks that seem to have mostly a negative impact (like gen V starters being revealed and the world discussing their legitimacy for so long that many people associate them as fakes to some degree, which has an inherent negative connotation to many people. or like how the whole gen 5 spritesheet was leaked, overwhelming everyone and triggering reactions it probably wouldnt have gotten if players were introduced to the creatures on a one by one basis, or at least hand-picked groups of ~5 diverse at a time as corocoro did often etc etc..)
Correct, I thought about the leaking thing after I posted.
In this case, I can see them revealing it in this month's Coro Coro anyway. Pokemon is totally random with how new games are revealed, and many game developers announce, reveal, and even show trailers of new stuff right before E3 as weird as it my be. So it's possible.