Without any foregoing announcement, Rockstar Games published another "Ballad Of Gay Tony" Video:

Furthermore, we could take some new information from the official Xbox 360 magazine:

• The Head-Up-Display (HUD) gets different colours: Pink, Green, Purple and yellow.
• The Ballad of Gay Tony consists of 20 missions!
• You can retry any mission to get 100% of the mission goal.
• There will be three night clubs named Bahama Mamas, Hercules und Maisonette 9. Luis, the main character will be able to manage the clubs Hercules and Maisonette 9.
• The golf course in Algonquin behind Memory Lanes will become visitable and there is a minigame: Golfing!
• New internet webpages
• Four mission names are already known: "Dropping In", "For the Man Who has Everything", "Going Deep" und "Sexy Time".

Thanks goes to Dennis from GTAnext.de for the information.