It's been three years since GTA IV came out, which means a lot of people are champing at the bit to see what comes next for Rockstar's signature franchise. Unfortunately, we're pretty sure you're going to have to keep waiting for the foreseeable future. Rockstar isn't on the E3 show floor in any official capacity, which means the company -- or any of the games its working on -- probably won't be there at all.
IGN director has said that "we know when GTA V will be announced and released". People can believe on IGN as IGN is one of the few trusted gaming sites that report genuine news. They wouldn't destruct their credibility especially a director. Some more trusted individual in the gaming media already knows what coming next.
http://games.ign.com/articles/116/1169657p1.html