User blog comment:RainingPain17/New GTA Online update revealed/@comment-25368842-20150603102955/@comment-25261281-20150603220846

Truth is Rockstar seems to forget GTA V and put all their stuff in Online. Conclusion: singleplayer is left behind. Why? Because in R*'s mind it is "ever1 playz online so lets do stuff 4 them". No, every GTA player doesn't fucking play GTA Online all-day. Therefore there is no justification for leaving GTA V behind while Online gets all the things, and online players are forced to buy a car to test it, as they cannot get it in SP beforehand. There is absolutely no particular reason to release new stuff for GTA Online and nada for GTA V.

With the Heists Update, all hopes for a singleplayer DLC were lost.