"We know many fans have been eagerly awaiting the release of the Online Heists that we had planned to release for you this spring, and they are taking more time to create than originally anticipated. We are very sorry for the delay, and are working hard to bring them to you as soon as we can. Please know that we are focused as always on making the best possible content for you to play and we are thankful to all of you for your patience, understanding and support. Stay tuned for more information on that as well as lots of other ongoing content updates, enhancements and additions to the world of GTA Online that are on the way."
There's no word yet on when exactly the feature will be implemented, but it sounds like the team at Rockstar is making it one of their heist priorities.