Thanks to modding team OpenIV, GTA IV’s Liberty city will be coming to GTA V very soon. There is no release date as at this moment but the modding team is said to have been working on this update since 2015.
Right now, all there is of this update is a teaser trailer which can be viewed at OpenIV. Liberty city is not going to replace Los Santos, keep in mind, instead it is going to exist alongside Los Santos and will be on the other side of the ocean.
Since the modding team don’t have the rights to GTA IV, what they are going to do is release a mod tool which extracts GTA IV’s Liberty city into Los Santos and for this, the players would need both a copy of GTA IV and GTA V.
According to the trailer, it seems you will have to use a plane to access Liberty city from Los Santos after the extraction. To view more about this, you can check out OpenIV.
With this mod, the selling rate of GTA V and IV will definitely increase even though they continue to sell very well till date.