If you mean in this site, the KH Insider staff said that spoilers are only allowed in the spoiler section and with spoiler tags, at least during the first three months from release. That would end April 29th. Then you will be able to post plot related content on the main section of the forums. And you can post anything else freely without the 3 months restriction, as long as it is not a spoiler, such as gameplay related topics.
If you mean on the Internet as a whole then... you know. You'll never be able to say anything without someone complaining about spoilers, no matter how old the spoiler is. A few days ago I read a not that old comment on youtube from someone complaining about the spoilers of Aerith's fate in FF7. It was a FF7 OST video with Aerith's theme. So yeah, what were they expecting to read in the comment section? It'll be the same for KH3.
Edit: I didn't see that Spockanort already told you about the 3 months. My bad.