There will be a special graphical preset for VR use, however the game will be playable in "regular mode" without a VR headset. The single player mode will be updated with all of the vehicles, weapons, clothes and all other non-multiplayer reliant content up to and including GTA Online's Lowriders: Custom Classics DLC — no need for mods to get Benny's into story mode anymore.
When playing in VR mode, gameplay will be locked into first-person mode. Rockstar has also implemented various new mechanics to make use of the capabilities of VR. Flashes of light and staring into the sun can temporarily "blind" the player, PEDs will dynamically react based on pre-scripted behavior profiles if you look directly at them and melee attacks will occasionally result in a dazed effect, blurring the player's vision for a few seconds.
There will also be select jobs in the Online component of GTA Vr which aren't available on previous version, or when not playing in VR mode. These jobs and missions were specifically developed to showcase the capabilities of VR with intuitive game mechanics and level design.
Rockstar knows that it might be pissing off some players if they make them buy yet another full price version of GTA V, so any previous owner of GTA V with a linked Social Club account can apply for a 60% discount coupon through Rockstar Support starting this August. As a standalone, GTA Vr will cost regular AAA full price, meaning $60. Certain Playstation VR bundles will give it either for free or at a lowered price, depending on retailer.
Playstation VR will be launching this October and already has a host of exclusive games announced. Since Microsoft's VR project is still a way away, GTA Vr is currently a Sony exclusive, though we can expect an Oculus Rift port soon enough. GTA Vr is the first truly AAA game to be announced for the new device and will probably be the biggest draw of sales — if predictions hold.
Rockstar has also teased that they littered the story mode of Vr with new, VR mode exclusive easter eggs, some of which may be crucial in solving the infamous "Mt. Chiliad Mystery", a string of easter eggs which are in some way linked to strange UFO sightings in GTA V.
So who's gonna be picking up GTA Vr when it launches!?