first off, your version of true happiness I don't see as being possible in human life. no one is going to be in that state do to the huge amount of variables that could go against that state so I see this as a completely theoretical. that being said, a huge part of the MDMA experience woud be missing even if one could reach this "true happiness" state and that is firstly the extreme euphoria provided by the MDMA. no matter how happy a person gets there is no way they can get to that level of euphoria without the chemical release in the brain only made possible by taking MDMA. Another huge part is the stimulant factor which plays a big part in the mood lift that occurs.
so even if this true happiness can be reached by a person they would only have one piece of the puzzle. The brain is not designed to release the nuerotransmitters in mass that are needed to produce the MDMA experince on its own and no amount of happiness or meditation or good vibes are going to change that.