We are now entering the month of May which means that Rockstar has a little over a month to release Heists in order for it to fall in line with their promise for a Spring release. Spring officially ends June 20th (Per AgentExeider's Tip: Rockstar considers Summer to end on June 1st) which means Rockstar has to release the High Life DLC and Heists by June 1st otherwise the content will be considered delayed.
Keep in mind that Heists were originally slated for release on Day 1 of GTA: Online. Shortly before GTA: Online's release Rockstar Stated that heists were delayed and coming soon after GTA: Online's release. Unless you consider around seven months later "soon" you could count Heists as having been delayed twice. Will Heists see a third delay? Vote above and discuss below.
Update: Now that it is summer, Heists have been delayed for the third time.
Rockstar has been confirmed to be working on a current gen game for release within a one year time frame, is this game GTA V on current gen? If so and if it is announced at E3, we may see a Heists announcement alongside it on Monday at E3. [SPECULATIVE]
Additionally, Battlefield which is a FPS War game, managed to get Heists before GTA: Online.