This is of course Red51's desire. He wants to get the game parallel so he can then force Java onto the backseat allowing Unity to take things from that point onwards.
In fact, I understood that he would like to focus first on NPCs, biomes and caves... But I think that having at least the basics of NPCs (bandits) would be enough to change the unity version to main.
I understand that there is still a lot to bring to the Unity version, but this can be done gradually and at the same time bring new features with each update, but just as important as this would be to deliver updates faster (even if they were smaller updates).