IGN are predicting the announcement of GTA V at the Electronic Entertainment Expo which runs June 7-9 2011. Rockstar has no significant presence at E3 this year, and we haven't heard much about an E3 reveal until recently, so we'll just have to wait and see what happens. For more information, make sure to tune into the Sony and Microsoft press conferences which can be seen live on the E3 website.
Press Conference Times
Microsoft: June 6, 9:30am US/PST
Sony: June 6, 5:00pm US/PST
See IGN's full list of E3 predictions here.