The features you have suggested can easily be implemented within the current RuneScape 3 game engine and client. There are also many core parts of RuneScape 3 to be completed (for example, mobile client, improvements to NXT, a browser version, etc.) so I wouldn't expect any mention of a successor for a long time. Even then though this version of the game should really just be branded 'RuneScape' and keep version/build numbers internal.Low on bank space? Click here.