This is due at 7pm Bst and 8pm EST.
As for what it could be about, it looks likely that it will at least in part be about the eshop as nintendo have announced it will be going through maintanence on the same day. Even more hopefully a german site has spotted a possible hint of GBA games to be arriving on the 3DS.
Or it could just be nintendo network unfied accounts and miiverse.
So, you hyped?