You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
ValveTime.co.uk | Valve News, Forums, Steam
Admittedly, it's a bit early to judge what GTAIV requires as yet, but there are some things that are easy to ask for without having played the game already.
I imagine there will be a new radio station or two.
Perhaps a new suburb with all new missions.
Some new cars and bikes.
The inclusion of planes (and parachutes), pushbikes, jetpacks and tanks?