Yachts, yachts, yachts. Every community portal dedicated to GTA Online, and even ones that aren't, are flooded with discussion of the new yachts which were added to the game via the recent Executives and Other Criminals DLC.
The buzz around the yachts is so powerful that is has even overpowered and stifled any conversation regarding the rather ground-breaking, revolutionary and significant VIP and Bodyguard system feature which also debuted with the update.
However, even so, with these super popular yachts only being five days old, players are already considering what the next similar addition to GTA Online should be, and the most logical evolution appears to be the idea of Recreational Vehciles, better known as simply "RVs". Luxurious mobile homes have had a small resurgence these past years in the appropriate circles, but are still hardly as widespread as yachts.

Since GTA Online got semi-mobile apartments on sea, it would be easy to assume that semi-mobile apartments on land will be coming next (with zeppelin like semi-mobile apartments in air...), in the form of high-end RVs.
Luxury ships already feature some display of engineering know-how, as the task of fitting specialized rooms and equipment into an object of a specific shape and size can be quite challenging, but cramming everything which would make a luxury home, well, luxurious into a road-legal vehicle, along with all the regular features of a van or truck seems almost impossible.