I don´t think we will be getting any "surprise" more than a new lovely Vision GT car plus some of the content that should be coming in the near future.
I will be happy to see some of the real "promises". (and hopefully the Senna content in May with no delay: possible kart track, Interlagos and some F1´s from that era, Lotus, Honda...):
Quote PD´s web site:
"Update:
These features will be implemented in future updates.
Community:
Players can create their own clubs, communicate with one another in the forums and organise race events for their members. It is possible to select from a private racing club, and a public racing club that is open to everyone. This feature will be added in a future update.
Quick Match:
This mode is for those who want to get in and race online right away. Matching is performed according to preset regulations, and the race will start when there are enough participants. This feature will be added in a future update.
B-Spec:
The B-spec mode is a mode where you give precision instructions to your driver. This popular feature from previous versions of GT will be added in a future update. Look forward to the new, more powerful B-Spec mode.
Course Maker:
This feature, available at a later stage through an update, will allow you to create your own custom tracks that can be driven in the game. Additionally, in another update we will add the possibility to generate a track by capturing the GPS coordinate data of a mobile app while you are driving that course. This GPS-generated tracks will be available in the game as playable content.
Data Logger:
This feature allows you to analyse your saved replay data to show Speed, Engine RPM, Throttle Input, Gear Position, Steering Angle, etc. in a graphical format. This feature will be added in a future update."
All from here (just scroll down):
http://www.gran-turismo.com/gb/products/gt6/
PS: It will be hilarious if at this point with the game "incomplete" they "give us" some paid DLC. (I got every DLC from GT5 even while I was not even playing it any more...this time I won´t get anything until they put all the content the game should have)