I know as of Melody of Memory, Yen Sid has commanded everyone to suspend their search for Sora, but in the KH4 trailer, we see Donald and Goofy looking for him still-- It's a highly specific hope, but I hope this is them sneaking off to search for a lead of their own. Now that Riku's also missing in Quadratum, D&G might be feeling like, as they did in Traverse Town, only they can find and help Sora.
If anything, it just seems like more interesting shit happens when Yen Sid is disobeyed and ignored. I haven't seen the old bitch make a plan that worked, so they might as well start ignoring him.
I'm expecting Sora to he a little hazy at first, not remembering where he came from or who his friends are, but knowing instinctually to use the Keyblade to help people. He's carrying the stress and impact of KH3's events, and the longing for his friends, but the faces and names might be fuzzy, as it seems something similar happened to Yozora, according to the Nameless Star.