If it leaks early, what do you think are the chances that the current emulators will actually be able to run it in a playable state?

Both Yuzu and Ryujinx were a crashy and glitchy unplayable mess when Arceus leaked, and Yuzu's team had the stance of "We will not support any game before it's release date" during that time.

But then again, Switch emulation is a lot further along now than it was before, and GameFreak being GameFreak they are probably re-using an engine from a previous now-working Pokemon game. But it could still have modifications.

Hell, they could intentionally even have fucked with it in ways they know will break current versions of Yuzu and Ryujinx.