This may sound strange, but theymos may use the Satoshi account to trick people into the tenth anniversary of the forum.
He has done a lot in April Fools so this trick will be amazing and it will make a lot of fuss.
I'd be highly disappointed if theymos would do this, and I expect the chance of this happening to be lower than the chance of
adding KYC.
As far as I know, satoshi's account is locked to prevent it from ever being abused, until Satoshi proves ownership.
Even if there is any announcement of KYC on the 10th anniversary, it will be a temporary thing as mentioned by theymos.
What else can be a forum feature which is not the prank either

I have exactly 3 plans for the 10th anniversary:
- Another thing which I will make public on Tuesday, probably. It's a temporary forum feature similar to past april fools things in some ways, though not a prank.