Over the last few years LDW has alternated their new games: VV2 - PT - VV3 - VF - VV4. Therefore it looks like the next game won't be a VV5, but either a second version of one of the others - FT, PT, or VF - or a completely new game. VF has proven extremely popular so my money would be on a VF2, but don't blame me if I'm wrong.

This post by Lukerie says that the title of VV4 will be "Virtual Villagers 4: The Tree of Life".

There is always the chance that VV4 will be the last in the series. Arthur has mentioned in the past that they've had the whole story mapped out from the start. What he hasn't said, however, is how many parts it will take to conclude the series. It might be that VV4 wraps up the whole tale completely.