There's no evidence that they were doing it for the shareholders other than the massive drought of information and the predicted bump in shares for the company. It's my opinion, of course, but I can't see any other reason for announcing it before sweeping it under the rug.
Check out this!
Non-GAAP Net Loss Per Diluted Share for Fiscal Year 2012 was $0.71
Company Expects Non-GAAP Net Income Per Diluted Share of $2.00 to $2.25 for Fiscal Year 2013
Take-2 needed to announce GTA V when it did so that its shareholders could see exactly why the company was predicting an increase such as this after such a poor year; shareholders of Take-2 may have assumed the company were expecting Borderlands, Bioshock, NBA 2K13 and XCOM to perform to GTA standards. I'm not too read-up on the stock market either but basically you don't get that kind of hike in profits unless you expect something big coming.
Edit: Back-tracked to some old sources and found this.
Take-Two share prices jumped 6% after GTA V's announcement.