I thought he had already announced. He already hit me up for a donation.
If I recall correctly, it was in November that Jindal said that he was exploring the possibility of running and he asked for donations and volunteers to indicate how much support he might have. He said at that time that he would make a decision after December. While there still has not been a formal public announcement, the email I received clearly references a campaign for governor and it is probably just a matter of time before an announcement is made.